Elasticity-based identification of tumor margins using Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Troyanova-Wood, Maria; Meng, Zhaokai; Yakovlev, Vladislav V.

2016-03-01

The purpose of this study is to demonstrate the efficacy of using Brillouin spectroscopy for differentiation between healthy and cancerous tissues. Previous studies of various cancers indicate that elasticity of the tumor differs from that of the surrounding tissue. We hypothesize that it is possible to distinguish between normal and malignant areas based on their Brillouin measurements. Brillouin spectroscopy is an emerging spectroscopic technique capable of assessing the local elasticity of samples by measuring the Brillouin shift. In the present study, we have used malignant melanoma tissue samples from Sinclair miniature swine to demonstrate the validity of our proposed application. We performed Brillouin measurements on healthy tissue, normal tumor and regressing tumor (as indicated by depigmentation of tissue). Overall, the tumors were found to be stiffer than the surrounding healthy tissue. However, the regressing tumor displayed the elastic properties closer to that of the healthy tissue. Based on the Brillouin measurements, we have successfully differentiated between the tumor and healthy tissues with a high degree of confidence (p<104 for normal tumor, p<0.05 for regressing tumor). Our results indicate that Brillouin spectroscopy is an appropriate tool to not only pinpoint tumor boundaries, but also to monitor tumor growth or evaluate its response to treatment.

Evaluation d’une grille de supervision des laboratoires des leishmanioses cutanées au Maroc

PubMed Central

El Mansouri, Bouchra; Amarir, Fatima; Hajli, Yamina; Fellah, Hajiba; Sebti, Faiza; Delouane, Bouchra; Sadak, Abderrahim; Adlaoui, El Bachir; Rhajaoui, Mohammed

2017-01-01

Introduction Afin d’évaluer une grille de contrôle standardisée de laboratoire de diagnostic des leishmanioses, comme nouveau outil de supervision. Méthodes Un essai pilote a été pratiqué sur sept laboratoires provinciaux, appartenant à quatre provinces au Maroc, en suivant l’évolution de leurs performances tous les deux ans, entre l’année 2006 et 2014. Cette étude détaille la situation des laboratoires provinciaux avant et après la mise en œuvre de la grille de supervision. Au total vingt et une grille sont analysées. Résultats En 2006, les résultats ont montré clairement une insuffisance des performances des laboratoires: besoin en formation (41.6%), personnel pratiquant le prélèvement cutané (25%), pénurie en matériels et réactifs (65%), gestions documentaire et local non conformes (85%). Différentes actions correctives ont été menées par le Laboratoire National de Référence des Leishmanioses (LNRL) durant la période d’étude. En 2014, le LNRL a enregistré une nette amélioration des performances des laboratoires. Les besoins en matière de formation, qualité du prélèvement, dotation en matériels et réactifs ont été comblés et une coordination efficace s’est établie entre le LNRL et les laboratoires provinciaux. Conclusion Ceci montre l'efficacité de la grille comme outil de supervision de grande qualité, et comme pierre angulaire de tout progrès qui doit être obtenu dans les programmes de lutte contre les leishmanioses. PMID:29187922

Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guoping, E-mail: guoping.lin@femto-st.fr; Diallo, Souleymane; Saleh, Khaldoun

2014-12-08

We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

Multi-wavelength Praseodymium fiber laser using stimulated Brillouin scattering

NASA Astrophysics Data System (ADS)

Ahmad, H.; Aidit, S. N.; Tiu, Z. C.

2018-02-01

A multi-wavelength Brillouin Praseodymium fiber laser (MWBPFL) operating at 1300 nm region is demonstrated based on the hybrid scheme by utilizing Brillouin gain medium and Praseodymium-doped fluoride fiber as linear gain medium. A 15 μm air gap is incorporated into the cavity to allow the switching of Brillouin frequency spacing from double to single spacing. Under the Brillouin pump of 8 dBm and the 1020 nm pump power of 567.2 mW, 36 Stokes lines with a wavelength spacing of 0.16 nm and 24 Stokes lines with a wavelength spacing of 0.08 nm are achieved. The wavelength tunability of 8 nm is realized for both MWBPFLs by shifting the Brillouin pump wavelength. The MWBPFLs exhibit an excellent stability in the number of generated Stokes and power level over one-hour period.

Intracavity brillouin scattering from passive Q-spoiling cells.

PubMed

Wick, R V; Guenther, A H

1968-01-01

Stimulated Brillouin scattering from the methanol solvent used in conjunction with cryptocyanine bleachable dye in a ruby laser cavity has been observed at low megawatt output powers. The frequency shifts of the Brillouin scattered radiation produced within the laser cavity are slightly less than frequency shifts produced in an external methanol cell. The Brillouin radiation was eliminated even at output power levels in excess of 250 MW when a 3-mm length cell was used in place of the 25.4-mm commercial cell.

High-reflectivity phase conjugation using Brillouin preamplification.

PubMed

Ridley, K D; Scott, A M

1990-07-15

We describe experiments in which a weak laser pulse is phase conjugated by using a high-gain Brillouin amplifier in front of a stimulated Brillouin scattering phase-conjugate mirror. We observe phase conjugation with signal energies as low as 3 x 10(-13) J and with a maximum reflection coefficient of 2 x 10(8).

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis.

PubMed

Remer, Itay; Cohen, Lear; Bilenca, Alberto

2017-09-22

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with <10 MHz spectral-resolution and <35 MHz Brillouin-shift measurement precision at <100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

Chaotic Brillouin optical correlation-domain analysis

NASA Astrophysics Data System (ADS)

Zhang, Jianzhong; Zhang, Mingtao; Zhang, Mingjiang; Liu, Yi; Feng, Changkun; Wang, Yahui; Wang, Yuncai

2018-04-01

We propose and experimentally demonstrate a chaotic Brillouin optical correlation-domain analysis (BOCDA) system for distributed fiber sensing. The utilization of the chaotic laser with low coherent state ensures high spatial resolution. The experimental results demonstrate a 3.92-cm spatial resolution over a 906-m measurement range. The uncertainty in the measurement of the local Brillouin frequency shift is 1.2MHz. The measurement signal-to-noise ratio is given, which is agreement with the theoretical value.

Recent Progress in Brillouin Scattering Based Fiber Sensors

PubMed Central

Bao, Xiaoyi; Chen, Liang

2011-01-01

Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures. PMID:22163842

Recent progress in Brillouin scattering based fiber sensors.

PubMed

Bao, Xiaoyi; Chen, Liang

2011-01-01

Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures.

Brillouin Study of the Quantization of Acoustic Modes in Nanospheres

NASA Astrophysics Data System (ADS)

Kuok, M. H.; Lim, H. S.; Ng, S. C.; Liu, N. N.; Wang, Z. K.

2003-06-01

The vibrational modes in three-dimensional ordered arrays of unembedded SiO2 nanospheres have been studied by Brillouin light scattering. Multiple distinct Brillouin peaks are observed whose frequencies are found to be inversely proportional to the diameter (≈200 340 nm) of the nanospheres, in agreement with Lamb’s theory. This is the first Brillouin observation of acoustic mode quantization in a nanoparticle arising from spatial confinement. The distinct spectral peaks measured afford an unambiguous assignment of seven surface and inner acoustic modes. Interestingly, the relative intensities and polarization dependence of the Brillouin spectrum do not agree with the predictions made for Raman scattering.

Brillouin study of the quantization of acoustic modes in nanospheres.

PubMed

Kuok, M H; Lim, H S; Ng, S C; Liu, N N; Wang, Z K

2003-06-27

The vibrational modes in three-dimensional ordered arrays of unembedded SiO2 nanospheres have been studied by Brillouin light scattering. Multiple distinct Brillouin peaks are observed whose frequencies are found to be inversely proportional to the diameter (approximately 200-340 nm) of the nanospheres, in agreement with Lamb's theory. This is the first Brillouin observation of acoustic mode quantization in a nanoparticle arising from spatial confinement. The distinct spectral peaks measured afford an unambiguous assignment of seven surface and inner acoustic modes. Interestingly, the relative intensities and polarization dependence of the Brillouin spectrum do not agree with the predictions made for Raman scattering.

Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

NASA Astrophysics Data System (ADS)

Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

2018-06-01

Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

My Great Migration from Sierra Leone

ERIC Educational Resources Information Center

Harvard Educational Review, 2011

2011-01-01

This article presents the author's personal narrative as an immigrant from Sierra Leone who has undergone so many challenges in life and ended up turning all these obstacles into opportunities. In this article, the author describes his life growing up in Sierra Leone, his first experience of the horrors of war, his life as a student, and his dream…

Obituary: Leon Van Speybroeck, 1935-2002

NASA Astrophysics Data System (ADS)

Gorenstein, Paul; Tananbaum, Harvey Dale

2003-12-01

Leon Van Speybroeck, a master designer of X-ray telescope mirrors and the telescope scientist for the Chandra X-ray Observatory, died in Newton, Massachusetts, on 25 December 2002, shortly after learning that he had metastatic melanoma. Leon was born on 27 August 1935 in Wichita, Kansas. His father, Paul, was Assistant Treasurer and head of the accounting department at Beech Aircraft, and his mother, Anna Florence (Utley), was a homemaker. Both parents died in 1996. Leon's younger sister, Saundra, is a nurse and his younger brother, John, is a surgeon. Leon received a BS in 1957 and a PhD in 1965, both in physics, from MIT. His PhD thesis, ``Elastic Electron-Deuteron Scattering at High Momentum Transfer," was carried out under the supervision of Henry Kendall and Jerome Friedman. Leon spent two more years at MIT as a research associate. In 1967, he was hired by American Science and Engineering (AS&E) in Cambridge, Massachusetts, and joined the X-ray astronomy group led by Riccardo Giacconi, who received the 2002 Nobel Prize in Physics for contributions to astrophysics that led to the discovery of cosmic X-ray sources. Leon soon became involved in the design and construction of high-resolution, grazing-incidence X-ray telescopes, starting with the Apollo Telescope Mount flown on NASA's Skylab from 1973 to 1974. A series of high-resolution X-ray images of the solar corona led to dramatic changes in ideas about the solar corona, with new emphasis on magnetic dynamo processes. When the Smithsonian Astrophysical Observatory and the Harvard College Observatory morphed into the Harvard-Smithsonian Center for Astrophysics (CfA) in 1973, Leon, with Giacconi and other senior X-ray astronomers from AS&E, joined the CfA and formed the high-energy astrophysics division. Leon guided the design and development of the X-ray mirrors on NASA's Einstein Observatory, which was flown from 1978 to 1981 as the first cosmic X-ray observatory with an imaging telescope. Along the way, he

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

NASA Astrophysics Data System (ADS)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Modeling of the competition of stimulated Raman and Brillouin scatter in multiple beam experiments

NASA Astrophysics Data System (ADS)

Cohen, Bruce I.; Baldis, Hector A.; Berger, Richard L.; Estabrook, Kent G.; Williams, Edward A.; Labaune, Christine

2001-02-01

Multiple laser beam experiments with plastic target foils at the Laboratoire pour L'Utilisation des Lasers Intenses (LULI) facility [Baldis et al., Phys. Rev. Lett. 77, 2957 (1996)] demonstrated anticorrelation of stimulated Brillouin and Raman backscatter (SBS and SRS). Detailed Thomson scattering diagnostics showed that SBS always precedes SRS, that secondary electron plasma waves sometimes accompanied SRS appropriate to the Langmuir Decay Instability (LDI), and that, with multiple interaction laser beams, the SBS direct backscatter signal in the primary laser beam was reduced while the SRS backscatter signal was enhanced and occurred earlier in time. Analysis and numerical calculations are presented here that evaluate the influences on the competition of SBS and SRS, of local pump depletion in laser hot spots due to SBS, of mode coupling of SBS and LDI ion waves, and of optical mixing of secondary and primary laser beams. These influences can be significant. The calculations take into account simple models of the laser beam hot-spot intensity probability distributions and assess whether ponderomotive and thermal self-focusing are significant. Within the limits of the model, which omits several other potentially important nonlinearities, the calculations suggest the effectiveness of local pump depletion, ion wave mode coupling, and optical mixing in affecting the LULI observations.

Stimulated Brillouin Scattering: its Generation and Applications in Optical Fibre

NASA Astrophysics Data System (ADS)

Culverhouse, David

1992-01-01

Available from UMI in association with The British Library. In the work presented in this thesis, the generation of stimulated Brillouin scattering and its applications in optical fibres is theoretically and experimentally investigated. The study pursues three special cases: (i) Backward stimulated Brillouin scattering in long fibre lengths; (ii) Backward stimulated Brillouin scattering in high finesse all fibre ring resonators; (iii) Forward stimulated Brillouin scattering in dual moded single core fibres. Stimulated Brillouin scattering (SBS) occurs for relatively low input powers in monomode optical fibres, as the power density is very high because of the relatively small core size. For applications such as optical communications, SBS is seen as a potentially deleterious effect because it can limit the maximum optical power transmitted by the fibre and hence decrease the distance between repeaters. SBS, however, can also be used to advantage in optical fibres, for example to produce amplification. In this thesis the comprehensive study of SBS in relation to other non-linear scattering mechanisms in optical fibres leads to the derivation of explicit definitions for the Brillouin gain and the Brillouin threshold. The study of SBS in high finesse all fibre ring resonators also demonstrates how threshold powers can be reduced, typically, from milliwatts observed in long fibre lengths to microwatts. Because Brillouin scattering is primarily a result of the interaction of the incident optical beam with spontaneously generated (thermal) fluctuations in the density of the medium, the spectral features show a considerable variation with temperature thus providing a mechanism with sufficient sensitivity to realise tunable microwave generation and frequency shifting devices. Finally, the observation of stimulated Brillouin scattering in a forward direction (FSBS) in dual moded single-core fibre is also reported. Frequency shifts in the order of 17MHz are observed in

High-extinction virtually imaged phased array-based Brillouin spectroscopy of turbid biological media

NASA Astrophysics Data System (ADS)

Fiore, Antonio; Zhang, Jitao; Shao, Peng; Yun, Seok Hyun; Scarcelli, Giuliano

2016-05-01

Brillouin microscopy has recently emerged as a powerful technique to characterize the mechanical properties of biological tissue, cell, and biomaterials. However, the potential of Brillouin microscopy is currently limited to transparent samples, because Brillouin spectrometers do not have sufficient spectral extinction to reject the predominant non-Brillouin scattered light of turbid media. To overcome this issue, we combined a multi-pass Fabry-Perot interferometer with a two-stage virtually imaged phased array spectrometer. The Fabry-Perot etalon acts as an ultra-narrow band-pass filter for Brillouin light with high spectral extinction and low loss. We report background-free Brillouin spectra from Intralipid solutions and up to 100 μm deep within chicken muscle tissue.

Ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation.

PubMed

Guo, Changlei; Che, Kaijun; Cai, Zhiping; Liu, Shuai; Gu, Guoqiang; Chu, Chengxu; Zhang, Pan; Fu, Hongyan; Luo, Zhengqian; Xu, Huiying

2015-11-01

We experimentally demonstrate an ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation in a high-Q silica microsphere resonator. The threshold of the Brillouin microlaser is as low as 8 μW, which is close to the theoretical prediction. Moreover, the fifth-order Stokes line with a frequency shift up to 55 GHz is achieved with a coupled pump power of less than 0.6 mW. Benefiting from resonant wavelength shifts driven by thermal dynamics in the microsphere, we further realized tunable microwave signals with tuning ranges of 40 MHz at an 11 GHz band and 20 MHz at a 22 GHz band. To the best of our knowledge, it was the first attempt for tunable microwave source based on the whispering-gallery-mode Brillouin microlaser. Such a tunable microwave source from a cascaded Brillouin microlaser could find significant applications in aerospace, communication engineering, and metrology.

Large On-Chip Amplification in Silicon via Forward Stimulated Brillouin Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kittlaus, Eric; Shin, Heedeuk; Rakich, Peter

2015-10-15

Strong Brillouin coupling has only recently been realized in silicon using a new class of op- tomechanical waveguides that yield both optical and phononic con nement. Despite these major advances, appreciable Brillouin ampli cation has yet to be observed in silicon. Using new membrane- suspended silicon waveguide we report large Brillouin ampli cation for the rst time, reaching levels greater than 5 dB for modest pump powers, and demonstrate a record low (5 mW) threshold for net ampli cation. This work represents a crucial advance necessary to realize high-performance Brillouin lasers and ampli ers in silicon.

Symposium on Turbulent Shear Flows (8th) Held in Munich, Germany on 9-11 September 1991. Volume 2. Sessions 19-31, Poster Sessions

DTIC Science & Technology

1991-09-01

FLAMES IN THE ATrR)S1]1 IERE USING A SECOND MOMNT TURBULENCE MODEL Hermilo RAMIREZ -LEON, Claude REY and Jean-Frangois SINI LABORATOIRE DE MECANIQUE DES...65 directly satisfied by an extended version of the C= F , ax6 aX5 artificial compressibility implicit method ( Ramirez -Leon et al,, 1991). 08 2 IR ap...the isotropization-of-production concept. For the compressible fluid case, Ramirez -Leon et al (1990) With regard to Eq (2), the right-hand side of

Sierra Leone Estuary

NASA Image and Video Library

2014-02-05

This image acquired by NASA Terra spacecraft is of the Sierra Leone estuary, which became a focal point for trade and interaction between Africans and Europeans because of its exceptional harbor, starting in the mid-15th century.

Energetic radiation influence on temperature dependency of Brillouin frequency in optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pheron, X.; Ouerdane, Y.; Delepine-Lesoille, S.

We present a post mortem study of the influence of energetic radiation on optical fiber Brillouin sensors, both Brillouin spectrum and its temperature dependency in two different fibers, a photosensitive optical fiber and a SMF28. The target application is nuclear wastes repository monitoring where optical fiber Brillouin sensors might be exposed to energetic radiation. UV exposure induced optical losses, Brillouin frequency shifts up to 28 MHz and even a variation of the temperature dependency. The photosensitive optical fiber resulted more sensitive than SMF28{sup TM}. (authors)

Short-pulse amplification by strongly coupled stimulated Brillouin scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, Matthew R., E-mail: mredward@princeton.edu; Mikhailova, Julia M.; Jia, Qing

2016-08-15

We examine the feasibility of strongly coupled stimulated Brillouin scattering as a mechanism for the plasma-based amplification of sub-picosecond pulses. In particular, we use fluid theory and particle-in-cell simulations to compare the relative advantages of Raman and Brillouin amplification over a broad range of achievable parameters.

Effects of pump recycling technique on stimulated Brillouin scattering threshold: a theoretical model.

PubMed

Al-Asadi, H A; Al-Mansoori, M H; Ajiya, M; Hitam, S; Saripan, M I; Mahdi, M A

2010-10-11

We develop a theoretical model that can be used to predict stimulated Brillouin scattering (SBS) threshold in optical fibers that arises through the effect of Brillouin pump recycling technique. Obtained simulation results from our model are in close agreement with our experimental results. The developed model utilizes single mode optical fiber of different lengths as the Brillouin gain media. For 5-km long single mode fiber, the calculated threshold power for SBS is about 16 mW for conventional technique. This value is reduced to about 8 mW when the residual Brillouin pump is recycled at the end of the fiber. The decrement of SBS threshold is due to longer interaction lengths between Brillouin pump and Stokes wave.

In Vivo Brillouin Analysis of the Aging Crystalline Lens

PubMed Central

Besner, Sebastien; Scarcelli, Giuliano; Pineda, Roberto; Yun, Seok-Hyun

2016-01-01

Purpose To analyze the age dependence of the longitudinal modulus of the crystalline lens in vivo using Brillouin scattering data in healthy subjects. Methods Brillouin scans were performed along the crystalline lens in 56 eyes from 30 healthy subjects aged from 19 to 63 years. Longitudinal elastic modulus was acquired along the sagittal axis of the lens with a transverse and axial resolution of 4 and 60 μm, respectively. The relative lens stiffness was computed, and correlations with age were analyzed. Results Brillouin axial profiles revealed nonuniform longitudinal modulus within the lens, increasing from a softer periphery toward a stiffer central plateau at all ages. The longitudinal modulus at the central plateau showed no age dependence in a range of 19 to 45 years and a slight decrease with age from 45 to 63 years. A significant intersubject variability was observed in an age-matched analysis. Importantly, the extent of the central stiff plateau region increased steadily over age from 19 to 63 years. The slope of change in Brillouin modulus in the peripheral regions were nearly age-invariant. Conclusions The adult human lens showed no measurable age-related increase in the peak longitudinal modulus. The expansion of the stiff central region of the lens is likely to be the major contributing factor to age-related lens stiffening. Brillouin microscopy may be useful in characterizing the crystalline lens for the optimization of surgical or pharmacological treatments aimed at restoring accommodative power. PMID:27699407

In Vivo Brillouin Analysis of the Aging Crystalline Lens.

PubMed

Besner, Sebastien; Scarcelli, Giuliano; Pineda, Roberto; Yun, Seok-Hyun

2016-10-01

To analyze the age dependence of the longitudinal modulus of the crystalline lens in vivo using Brillouin scattering data in healthy subjects. Brillouin scans were performed along the crystalline lens in 56 eyes from 30 healthy subjects aged from 19 to 63 years. Longitudinal elastic modulus was acquired along the sagittal axis of the lens with a transverse and axial resolution of 4 and 60 μm, respectively. The relative lens stiffness was computed, and correlations with age were analyzed. Brillouin axial profiles revealed nonuniform longitudinal modulus within the lens, increasing from a softer periphery toward a stiffer central plateau at all ages. The longitudinal modulus at the central plateau showed no age dependence in a range of 19 to 45 years and a slight decrease with age from 45 to 63 years. A significant intersubject variability was observed in an age-matched analysis. Importantly, the extent of the central stiff plateau region increased steadily over age from 19 to 63 years. The slope of change in Brillouin modulus in the peripheral regions were nearly age-invariant. The adult human lens showed no measurable age-related increase in the peak longitudinal modulus. The expansion of the stiff central region of the lens is likely to be the major contributing factor to age-related lens stiffening. Brillouin microscopy may be useful in characterizing the crystalline lens for the optimization of surgical or pharmacological treatments aimed at restoring accommodative power.

The effect of pressure on spontaneous Rayleigh-Brillouin scattering spectrum in nitrogen

NASA Astrophysics Data System (ADS)

Yang, Chuanyin; Wu, Tao; Shang, Jingcheng; Zhang, Xinyi; Hu, Rongjing; He, XingDao

2018-05-01

In order to study the effect of gas pressure on spontaneous Rayleigh-Brillouin scattering spectrum and verify the validity of Tenti S6 model at pressures up to 8 atm, the spontaneous Rayleigh-Brillouin scattering experiment in nitrogen was performed for a wavelength of 532 nm at the constant room temperature of 296 K and a 90° scattering angle. By comparing the experimental spectrum with the theoretical spectrum, the normalized root mean square deviation was calculated and found less than 2.2%. It is verified that Tenti S6 model can be applied to the spontaneous Rayleigh-Brillion scattering of nitrogen under higher pressures. The results of the experimental data analysis demonstrate that pressure has more effect on Brillouin peak intensity and has negligible effect on Brillouin frequency shift, and pressure retrieval based on spontaneous Rayleigh-Brillouin scattering profile is a promising method for remote of pressure, such as harsh environment applications. Some factors that caused experiment deviations are also discussed.

Ebola Virus Disease--Sierra Leone and Guinea, August 2015.

PubMed

Hersey, Sara; Martel, Lise D; Jambai, Amara; Keita, Sakoba; Yoti, Zabulon; Meyer, Erika; Seeman, Sara; Bennett, Sarah; Ratto, Jeffrey; Morgan, Oliver; Akyeampong, Mame Afua; Sainvil, Schabbethai; Worrell, Mary Claire; Fitter, David; Arnold, Kathryn E

2015-09-11

The Ebola virus disease (Ebola) outbreak in West Africa began in late 2013 in Guinea (1) and spread unchecked during early 2014. By mid-2014, it had become the first Ebola epidemic ever documented. Transmission was occurring in multiple districts of Guinea, Liberia, and Sierra Leone, and for the first time, in capital cities (2). On August 8, 2014, the World Health Organization (WHO) declared the outbreak to be a Public Health Emergency of International Concern (3). Ministries of Health, with assistance from multinational collaborators, have reduced Ebola transmission, and the number of cases is now declining. While Liberia has not reported a case since July 12, 2015, transmission has continued in Guinea and Sierra Leone, although the numbers of cases reported are at the lowest point in a year. In August 2015, Guinea and Sierra Leone reported 10 and four confirmed cases, respectively, compared with a peak of 526 (Guinea) and 1,997 (Sierra Leone) in November 2014. This report details the current situation in Guinea and Sierra Leone, outlines strategies to interrupt transmission, and highlights the need to maintain public health response capacity and vigilance for new cases at this critical time to end the outbreak.

Modeling and evaluating the performance of Brillouin distributed optical fiber sensors.

PubMed

Soto, Marcelo A; Thévenaz, Luc

2013-12-16

A thorough analysis of the key factors impacting on the performance of Brillouin distributed optical fiber sensors is presented. An analytical expression is derived to estimate the error on the determination of the Brillouin peak gain frequency, based for the first time on real experimental conditions. This expression is experimentally validated, and describes how this frequency uncertainty depends on measurement parameters, such as Brillouin gain linewidth, frequency scanning step and signal-to-noise ratio. Based on the model leading to this expression and considering the limitations imposed by nonlinear effects and pump depletion, a figure-of-merit is proposed to fairly compare the performance of Brillouin distributed sensing systems. This figure-of-merit offers to the research community and to potential users the possibility to evaluate with an objective metric the real performance gain resulting from any proposed configuration.

Revealing the glass transition in shape memory polymers using Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Steelman, Zachary A.; Weems, Andrew C.; Traverso, Andrew J.; Szafron, Jason M.; Maitland, Duncan J.; Yakovlev, Vladislav V.

2017-12-01

Emerging medical devices which employ shape memory polymers (SMPs) require precise measurements of the glass transition temperature (Tg) to ensure highly controlled shape recovery kinetics. Conventional techniques like differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) have limitations that prevent utilization for certain devices, including limited accuracy and the need for sacrificial samples. In this report, we employ an approach based on Brillouin spectroscopy to probe the glass transition of SMPs rapidly, remotely, and nondestructively. Further, we compare the Tg obtained from Brillouin scattering with DMA- and DSC-measured Tg to demonstrate the accuracy of Brillouin scattering for this application. We conclude that Brillouin spectroscopy is an accurate technique for obtaining the glass transition temperature of SMPs, aligning closely with the most common laboratory standards while providing a rapid, remote, and nondestructive method for the analysis of unique polymeric medical devices.

Revealing the glass transition in shape memory polymers using Brillouin spectroscopy.

PubMed

Steelman, Zachary A; Weems, Andrew C; Traverso, Andrew J; Szafron, Jason M; Maitland, Duncan J; Yakovlev, Vladislav V

2017-12-11

Emerging medical devices which employ shape memory polymers (SMPs) require precise measurements of the glass transition temperature (T g ) to ensure highly controlled shape recovery kinetics. Conventional techniques like differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) have limitations that prevent utilization for certain devices, including limited accuracy and the need for sacrificial samples. In this report, we employ an approach based on Brillouin spectroscopy to probe the glass transition of SMPs rapidly, remotely, and nondestructively. Further, we compare the T g obtained from Brillouin scattering with DMA- and DSC-measured T g to demonstrate the accuracy of Brillouin scattering for this application. We conclude that Brillouin spectroscopy is an accurate technique for obtaining the glass transition temperature of SMPs, aligning closely with the most common laboratory standards while providing a rapid, remote, and nondestructive method for the analysis of unique polymeric medical devices.

Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre

PubMed Central

Beugnot, Jean-Charles; Lebrun, Sylvie; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

2014-01-01

Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of Brillouin light scattering from surface acoustic waves. These Rayleigh-type surface waves travel the wire surface at a specific velocity of 3,400 m s−1 and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics. PMID:25341638

Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber.

PubMed

Tchahame, Joël Cabrel; Beugnot, Jean-Charles; Kudlinski, Alexandre; Sylvestre, Thibaut

2015-09-15

We investigate the stimulated Brillouin scattering (SBS) in a long tapered birefringent solid-core photonic crystal fiber (PCF) and compare our results with a similar but untapered PCF. It is shown that the taper generates a broadband and multipeaked Brillouin spectrum, while significantly increasing the threshold power. Furthermore, we observe that the strong fiber birefringence gives rise to a frequency shift of the Brillouin spectrum which increases along the fiber. Numerical simulations are also presented to account for the taper effect and the birefringence. Our findings open a new means to control or inhibit the SBS by tapering photonic crystal fibers.

Lassa fever in post-conflict sierra leone.

PubMed

Shaffer, Jeffrey G; Grant, Donald S; Schieffelin, John S; Boisen, Matt L; Goba, Augustine; Hartnett, Jessica N; Levy, Danielle C; Yenni, Rachael E; Moses, Lina M; Fullah, Mohammed; Momoh, Mambo; Fonnie, Mbalu; Fonnie, Richard; Kanneh, Lansana; Koroma, Veronica J; Kargbo, Kandeh; Ottomassathien, Darin; Muncy, Ivana J; Jones, Abigail B; Illick, Megan M; Kulakosky, Peter C; Haislip, Allyson M; Bishop, Christopher M; Elliot, Deborah H; Brown, Bethany L; Zhu, Hu; Hastie, Kathryn M; Andersen, Kristian G; Gire, Stephen K; Tabrizi, Shervin; Tariyal, Ridhi; Stremlau, Mathew; Matschiner, Alex; Sampey, Darryl B; Spence, Jennifer S; Cross, Robert W; Geisbert, Joan B; Folarin, Onikepe A; Happi, Christian T; Pitts, Kelly R; Geske, F Jon; Geisbert, Thomas W; Saphire, Erica Ollmann; Robinson, James E; Wilson, Russell B; Sabeti, Pardis C; Henderson, Lee A; Khan, S Humarr; Bausch, Daniel G; Branco, Luis M; Garry, Robert F

2014-03-01

Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF.

Highly localized distributed Brillouin scattering response in a photonic integrated circuit

NASA Astrophysics Data System (ADS)

Zarifi, Atiyeh; Stiller, Birgit; Merklein, Moritz; Li, Neuton; Vu, Khu; Choi, Duk-Yong; Ma, Pan; Madden, Stephen J.; Eggleton, Benjamin J.

2018-03-01

The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit. This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift and linewidth, essential information for the further development of high quality photonic-phononic waveguides for SBS applications.

Stability of Brillouin flow in planar, conventional, and inverted magnetrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, D. H.; Lau, Y. Y.; Greening, G.

2015-08-15

The Brillouin flow is the prevalent flow in crossed-field devices. We systematically study its stability in the conventional, planar, and inverted magnetron geometry. To investigate the intrinsic negative mass effect in Brillouin flow, we consider electrostatic modes in a nonrelativistic, smooth bore magnetron. We found that the Brillouin flow in the inverted magnetron is more unstable than that in a planar magnetron, which in turn is more unstable than that in the conventional magnetron. Thus, oscillations in the inverted magnetron may startup faster than the conventional magnetron. This result is consistent with simulations, and with the negative mass property inmore » the inverted magnetron configuration. Inclusion of relativistic effects and electromagnetic effects does not qualitatively change these conclusions.« less

Brillouin Optomechanics in Coupled Silicon Microcavities

NASA Astrophysics Data System (ADS)

Espinel, Y. A. V.; Santos, F. G. S.; Luiz, G. O.; Alegre, T. P. Mayer; Wiederhecker, G. S.

2017-03-01

The simultaneous control of optical and mechanical waves has enabled a range of fundamental and technological breakthroughs, from the demonstration of ultra-stable frequency reference devices, to the exploration of the quantum-classical boundaries in optomechanical laser-cooling experiments. More recently, such an optomechanical interaction has been observed in integrated nano-waveguides and microcavities in the Brillouin regime, where short-wavelength mechanical modes scatter light at several GHz. Here we engineer coupled optical microcavities to enable a low threshold excitation of mechanical travelling-wave modes through backward stimulated Brillouin scattering. Exploring the backward scattering we propose silicon microcavity designs based on laterally coupled single and double-layer cavities, the proposed structures enable optomechanical coupling with very high frequency modes (11 to 25 GHz) and large optomechanical coupling rates (g0/2π) from 50 kHz to 90 kHz.

RTEMS SMP and MTAPI for Efficient Multi-Core Space Applications on LEON3/LEON4 Processors

NASA Astrophysics Data System (ADS)

Cederman, Daniel; Hellstrom, Daniel; Sherrill, Joel; Bloom, Gedare; Patte, Mathieu; Zulianello, Marco

2015-09-01

This paper presents the final result of an European Space Agency (ESA) activity aimed at improving the software support for LEON processors used in SMP configurations. One of the benefits of using a multicore system in a SMP configuration is that in many instances it is possible to better utilize the available processing resources by load balancing between cores. This however comes with the cost of having to synchronize operations between cores, leading to increased complexity. While in an AMP system one can use multiple instances of operating systems that are only uni-processor capable, a SMP system requires the operating system to be written to support multicore systems. In this activity we have improved and extended the SMP support of the RTEMS real-time operating system and ensured that it fully supports the multicore capable LEON processors. The targeted hardware in the activity has been the GR712RC, a dual-core core LEON3FT processor, and the functional prototype of ESA's Next Generation Multiprocessor (NGMP), a quad core LEON4 processor. The final version of the NGMP is now available as a product under the name GR740. An implementation of the Multicore Task Management API (MTAPI) has been developed as part of this activity to aid in the parallelization of applications for RTEMS SMP. It allows for simplified development of parallel applications using the task-based programming model. An existing space application, the Gaia Video Processing Unit, has been ported to RTEMS SMP using the MTAPI implementation to demonstrate the feasibility and usefulness of multicore processors for space payload software. The activity is funded by ESA under contract 4000108560/13/NL/JK. Gedare Bloom is supported in part by NSF CNS-0934725.

Meson and baryon dispersion relations with Brillouin fermions

NASA Astrophysics Data System (ADS)

Dürr, Stephan; Koutsou, Giannis; Lippert, Thomas

2012-12-01

We study the dispersion relations of mesons and baryons built from Brillouin quarks on one Nf=2 gauge ensemble provided by QCDSF. For quark masses up to the physical strange quark mass, there is hardly any improvement over the Wilson discretization, if either action is link-smeared and tree-level clover improved. For quark masses in the range of the physical charm quark mass, the Brillouin action still shows a perfect relativistic behavior, while the Wilson action induces severe cutoff effects. As an application we determine the masses of the Ωc0, Ωcc+ and Ωccc++ baryons on that ensemble.

Stimulated Brillouin scattering of laser in semiconductor plasma embedded with nano-sized grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Giriraj, E-mail: grsharma@gmail.com; Dad, R. C.; Ghosh, S.

2015-07-31

A high power laser propagating through semiconductor plasma undergoes Stimulated Brillouin scattering (SBS) from the electrostrictively generated acoustic perturbations. We have considered that nano-sized grains (NSGs) ions are embedded in semiconductor plasma by means of ion implantation. The NSGs are bombarded by the surrounding plasma particles and collect electrons. By considering a negative charge on the NSGs, we present an analytically study on the effects of NSGs on threshold field for the onset of SBS and Brillouin gain of generated Brillouin scattered mode. It is found that as the charge on the NSGs builds up, the Brillouin gain is significantlymore » raised and the threshold pump field for the onset of SBS process is lowered.« less

Demonstration of highly efficient forward stimulated Brillouin scattering in partly suspended silicon nanowire racetrack resonators

NASA Astrophysics Data System (ADS)

Zhang, Ruiwen; Sun, Junqiang; Chen, Guodong; Cheng, Ming; Jiang, Jialin

2017-07-01

We demonstrate the forward stimulated Brillouin scattering (FSBS) in a partly suspended silicon nanowire racetrack resonator. To realize the tight confinement of the transverse acoustic modes in the nanoscale silicon core, the racetrack resonator is supported by the tiny pillar. The Brillouin amplification of 2.25 dB is achieved with the resonator radius of 100 μm under a low-power pump laser of 8 mW. The influences of the waveguide width and the top width of the tiny pillar on the Brillouin frequency shift and Brillouin gain are presented and analyzed. The Brillouin frequency shift is conveniently manipulated by the changes in waveguide widths. Our proposed approach furnishes an alternative towards harnessing FSBS in integrated photonic circuits.

High power, high signal-to-noise ratio single-frequency 1μm Brillouin all-fiber laser

NASA Astrophysics Data System (ADS)

Wang, Jing; Hou, Yubin; Zhang, Qian; Jin, Dongchen; Sun, Ruoyu; Shi, Hongxing; Liu, Jiang; Wang, Pu

2016-03-01

We demonstrate a high-power, high signal-to-noise ratio single-frequency 1 μm Brillouin all-fiber laser with high slope efficiency. The Brillouin laser system consists of a high-power single-frequency fiber laser and a single-pass Brillouin ring cavity. The high-power single-frequency fiber laser is one-stage master-oscillator power amplifier with the maximum output power of 10.33 W, the signal-to-noise ratio of 50 dB and the slope efficiency of 46%. The Brillouin fiber laser is pumped by the amplified laser with a linewidth of 33 kHz and an output power of 2.61 W limited by the damage threshold of the optical isolator. By optimizing the length of the Brillouin ring cavity to 10 m, stable singlefrequency Brillouin fiber laser is obtained with 3 kHz linewidth owing to the linewidth narrowing effect. At the launched pump power of 2.15 W, the Brillouin fiber laser generates maximum output power of 1.4 W with a slope efficiency of 79% and the optical signal-to-noise ratio of 77 dB.

Dual Raman-Brillouin spectroscopic investigation of plant stress response and development

NASA Astrophysics Data System (ADS)

Coker, Zachary; Troyanova-Wood, Maria; Marble, Kassie; Yakovlev, Vladislav

2018-03-01

Raman and Brillouin spectroscopy are powerful tools for non-invasive and non-destructive investigations of material chemical and mechanical properties. In this study, we use a newly developed custom-built dual Raman-Brillouin microspectroscopy instrument to build on previous works studying in-vivo stress response of live plants using only a Raman spectroscopy system. This dual Raman-Brillouin spectroscopy system is capable of fast simultaneous spectra acquisition from single-point locations. Shifts and changes in a samples Brillouin spectrum indicate a change in the physical characteristics of the sample, namely mechano-elasticity; in measuring this change, we can establish a relationship between the mechanical properties of a sample and known stress response agents, such as reactive oxygen species and other chemical constituents as indicated by peaks in the Raman spectra of the same acquisition point. Simultaneous application of these spectroscopic techniques offers great promise for future development and applications in agricultural and biological studies and can help to improve our understanding of mechanochemical changes of plants and other biological samples in response to environmental and chemically induced stresses at microscopic or cellular level.

Raman and Brillouin scattering studies of bulk 2H-WSe2

NASA Astrophysics Data System (ADS)

Akintola, K.; Andrews, G. T.; Curnoe, S. H.; Koehler, M. R.; Keppens, V.

2015-10-01

Raman and Brillouin spectroscopy were used to probe optic and acoustic phonons in bulk 2H-WSe2. Raman spectra collected under different polarization conditions allowed assignment of spectral peaks to various first- and second-order processes. In contrast to some previous studies, a Raman peak at  ˜259 cm-1was found not to be due to the A1g mode but to a second-order process involving phonons at either the M or K point of the Brillouin zone. Resonance effects due to excitons were also observed in the Raman spectra. Brillouin spectra of 2H-WSe2 contain a single peak doublet arising from a Rayleigh surface mode propagating with a velocity of 1340+/- 20 m s-1. This value is comparable to that estimated from Density Functional Theory calculations and also to those for the transition metal diselenides 2H-TaSe2 and 2H-NbSe2. Unlike these two materials, however, peaks arising from scattering via the elasto-optic mechanism were not observed in Brillouin spectra of WSe2 despite its lower opacity.

Using Brillouin microspectroscopy to characterize adipocytes' response to lipid droplet accumulation

NASA Astrophysics Data System (ADS)

Troyanova-Wood, Maria; Coker, Zachary; Traverso, Andrew; Yakovlev, Vladislav V.

2017-02-01

Obesity and overweight are accompanied by an enlargement of adipocytes, which is commonly related to the increasing number or size of lipid droplets within the cells. Some studies have shown that the accumulation of lipid droplets within adipocytes results in their increased stiffness. Recently, Brillouin microspectroscopy has been introduced as a nondestructive method of imaging the elasticity of cells. Unlike other imaging modalities, it is capable of assessing the elastic properties on both tissue- and cell levels. In this study, Brillouin spectroscopy was used to measure the elasticity changes in response to accumulation of lipid droplets within adipocyte during adipogenesis. The cell line used in the study is 3T3-L1, with chemically-induced differentiation from pre-adipocytes to mature adipocytes. The Brillouin shift measurements of the cells before and after differentiation indicate that the stiffness of adipocytes increases due to accumulation of lipid droplets. The results are in agreement with previous atomic force microscopy (AFM) nanoindentation studies. Brillouin microspectroscopy is a technique suitable for measuring the changes of elasticity of adipocytes in response to lipid droplet accumulation.

Lassa Fever in Post-Conflict Sierra Leone

PubMed Central

Hartnett, Jessica N.; Levy, Danielle C.; Yenni, Rachael E.; Moses, Lina M.; Fullah, Mohammed; Momoh, Mambo; Fonnie, Mbalu; Fonnie, Richard; Kanneh, Lansana; Koroma, Veronica J.; Kargbo, Kandeh; Ottomassathien, Darin; Muncy, Ivana J.; Jones, Abigail B.; Illick, Megan M.; Kulakosky, Peter C.; Haislip, Allyson M.; Bishop, Christopher M.; Elliot, Deborah H.; Brown, Bethany L.; Zhu, Hu; Hastie, Kathryn M.; Andersen, Kristian G.; Gire, Stephen K.; Tabrizi, Shervin; Tariyal, Ridhi; Stremlau, Mathew; Matschiner, Alex; Sampey, Darryl B.; Spence, Jennifer S.; Cross, Robert W.; Geisbert, Joan B.; Folarin, Onikepe A.; Happi, Christian T.; Pitts, Kelly R.; Geske, F. Jon; Geisbert, Thomas W.; Saphire, Erica Ollmann; Robinson, James E.; Wilson, Russell B.; Sabeti, Pardis C.; Henderson, Lee A.; Khan, S. Humarr; Bausch, Daniel G.; Branco, Luis M.; Garry, Robert F.

2014-01-01

Background Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. Methodology/Principal Findings Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. Conclusions/Significance Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to

Control of Brillouin short-pulse seed amplification by chirping the pump pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehmann, G.; Spatschek, K. H.

Seed amplification via Brillouin backscattering of a long pump pulse is considered. Similar to Raman amplification, several obstructive effects may occur during short-pulse Brillouin amplification. One is the spontaneous Raman backscattering of the pump before interacting with the seed. Preforming the plasma and/or chirping the pump will reduce unwanted pump backscattering. Optimized regions for low-loss pump propagation were proposed already in conjunction with Raman seed amplification. Hence, the influence of the chirp of the pump during Brillouin interaction with the seed becomes important and will be considered here. Both, the linear as well as the nonlinear evolution phases of themore » seed caused by Brillouin amplification under the action of a chirped pump are investigated. The amplification rate as well as the seed profiles are presented as function of the chirping rate. Also the dependence of superradiant scaling rates on the chirp parameter is discussed.« less

Biomechanical Changes After LASIK Flap Creation Combined With Rapid Cross-Linking Measured With Brillouin Microscopy.

PubMed

Randleman, J Bradley; Su, Johnny P; Scarcelli, Giuliano

2017-06-01

To evaluate the biomechanical changes occurring after LASIK flap creation and rapid corneal cross-linking (CXL) measured with Brillouin light microscopy. Porcine eyes (n = 11) were evaluated by Brillouin light microscopy sequentially in the following order: virgin state, after LASIK flap creation, and after rapid CXL. Each eye served as its own control. Depth profile of the Brillouin frequency shift was computed to reveal the depth-dependent changes in corneal stiffness. There was a statistically significant reduction of Brillouin shift (reduced corneal stiffness) after LASIK flap creation compared to virgin corneas across total corneal thickness (-0.035 GHz, P = .0195) and within the anterior stromal region (-0.104 GHz, P = .0039). Changes in the central (-0.029 GHz, P = .0391) and posterior (-0.005 GHz, P = .99) stromal regions were not significant. There was a small increase in Brillouin shift after rapid cross-linking that was not statistically or clinically significant across total corneal thickness (0.006 GHz, P = .4688 for any specific stromal region; 0.002 to 0.009 GHz, P > .46 for all). LASIK flap creation significantly reduced Brillouin shift in the anterior third of the stroma in porcine eyes. Rapid corneal cross-linking had no significant effect on Brillouin shift after LASIK flap creation in porcine eyes. With further validation, non-contact, non-perturbative Brillouin microscopy could become a useful monitoring tool to evaluate the biomechanical impact of corneal refractive procedures and corneal cross-linking protocols. [J Refract Surg. 2017;33(6):408-414.]. Copyright 2017, SLACK Incorporated.

Efficient dynamic events discrimination technique for fiber distributed Brillouin sensors.

PubMed

Galindez, Carlos A; Madruga, Francisco J; Lopez-Higuera, Jose M

2011-09-26

A technique to detect real time variations of temperature or strain in Brillouin based distributed fiber sensors is proposed and is investigated in this paper. The technique is based on anomaly detection methods such as the RX-algorithm. Detection and isolation of dynamic events from the static ones are demonstrated by a proper processing of the Brillouin gain values obtained by using a standard BOTDA system. Results also suggest that better signal to noise ratio, dynamic range and spatial resolution can be obtained. For a pump pulse of 5 ns the spatial resolution is enhanced, (from 0.541 m obtained by direct gain measurement, to 0.418 m obtained with the technique here exposed) since the analysis is concentrated in the variation of the Brillouin gain and not only on the averaging of the signal along the time. © 2011 Optical Society of America

Nonlinear Brillouin amplification of finite-duration seeds in the strong coupling regime

NASA Astrophysics Data System (ADS)

Lehmann, G.; Spatschek, K. H.

2013-07-01

Parametric plasma processes received renewed interest in the context of generating ultra-intense and ultra-short laser pulses up to the exawatt-zetawatt regime. Both Raman as well as Brillouin amplifications of seed pulses were proposed. Here, we investigate Brillouin processes in the one-dimensional (1D) backscattering geometry with the help of numerical simulations. For optimal seed amplification, Brillouin scattering is considered in the so called strong coupling (sc) regime. Special emphasis lies on the dependence of the amplification process on the finite duration of the initial seed pulses. First, the standard plane-wave instability predictions are generalized to pulse models, and the changes of initial seed pulse forms due to parametric instabilities are investigated. Three-wave-interaction results are compared to predictions by a new (kinetic) Vlasov code. The calculations are then extended to the nonlinear region with pump depletion. Generation of different seed layers is interpreted by self-similar solutions of the three-wave interaction model. Similar to Raman amplification, shadowing of the rear layers by the leading layers of the seed occurs. The shadowing is more pronounced for initially broad seed pulses. The effect is quantified for Brillouin amplification. Kinetic Vlasov simulations agree with the three-wave interaction predictions and thereby affirm the universal validity of self-similar layer formation during Brillouin seed amplification in the strong coupling regime.

Curriculum Diversification Re-examined--A Case Study of Sierra Leone.

ERIC Educational Resources Information Center

Wright, Cream A. H.

This paper deals with a case study of secondary curriculum diversification as a vocationalization strategy in Sierra Leone. It explores diversification issues from four crucial standpoints that are distinct but highly interrelated. First, diversification is dealt with as a policy that was adopted and actively pursued by Sierra Leone for over a…

Canonical angular momentum compression near the Brillouin limit

NASA Astrophysics Data System (ADS)

Jeong, E.; Gilson, E.; Fajans, J.

2000-10-01

Near the Brillouin limit, the angular momentum of a trapped, T=0, pure-electron plasma approaches zero. If the plasma expands axially, its density would appear to drop. However, the plasma's canonical angular momentum is not changed by an axial expansion, so the plasma must stay near the Brillouin limit; thus the plasma's density cannot change when it is expanded. The only way for the plasma density to remain constant as the plasma length increases is for the plasma radius to decrease. Dynamically, this decrease is caused by the polarization drift induced by a small decrease in the density. In this poster we present preliminary experimental evidence demonstrating this radial compression. This work was supported by the ONR.

Single-shot distributed Brillouin optical time domain analyzer.

PubMed

Fang, Jian; Xu, Pengbai; Dong, Yongkang; Shieh, William

2017-06-26

We demonstrate a novel single-shot distributed Brillouin optical time domain analyzer (SS-BOTDA). In our method, dual-polarization probe with orthogonal frequency-division multiplexing (OFDM) modulation is used to acquire the distributed Brillouin gain spectra, and coherent detection is used to enhance the signal-to-noise ratio (SNR) drastically. Distributed temperature sensing is demonstrated over a 1.08 km standard single-mode fiber (SSMF) with 20.48 m spatial resolution and 0.59 °C temperature accuracy. Neither frequency scanning, nor polarization scrambling, nor averaging is required in our scheme. All the data are obtained through only one-shot measurement, indicating that the sensing speed is only limited by the length of fiber.

USP5/Leon deubiquitinase confines postsynaptic growth by maintaining ubiquitin homeostasis through Ubiquilin.

PubMed

Wang, Chien-Hsiang; Huang, Yi-Chun; Chen, Pei-Yi; Cheng, Ying-Ju; Kao, Hsiu-Hua; Pi, Haiwei; Chien, Cheng-Ting

2017-05-10

Synapse formation and growth are tightly controlled processes. How synaptic growth is terminated after reaching proper size remains unclear. Here, we show that Leon, the Drosophila USP5 deubiquitinase, controls postsynaptic growth. In leon mutants, postsynaptic specializations of neuromuscular junctions are dramatically expanded, including the subsynaptic reticulum, the postsynaptic density, and the glutamate receptor cluster. Expansion of these postsynaptic features is caused by a disruption of ubiquitin homeostasis with accumulation of free ubiquitin chains and ubiquitinated substrates in the leon mutant. Accumulation of Ubiquilin (Ubqn), the ubiquitin receptor whose human homolog ubiquilin 2 is associated with familial amyotrophic lateral sclerosis, also contributes to defects in postsynaptic growth and ubiquitin homeostasis. Importantly, accumulations of postsynaptic proteins cause different aspects of postsynaptic overgrowth in leon mutants. Thus, the deubiquitinase Leon maintains ubiquitin homeostasis and proper Ubqn levels, preventing postsynaptic proteins from accumulation to confine postsynaptic growth.

An L-band multi-wavelength Brillouin-erbium fiber laser with switchable frequency spacing

NASA Astrophysics Data System (ADS)

Zhou, Xuefang; Hu, Kongwen; Wei, Yizhen; Bi, Meihua; Yang, Guowei

2017-01-01

In this paper, a novel L-band multi-wavelength Brillouin-erbium fiber laser consisting of two ring cavities is proposed and demonstrated. The frequency spacing can be switched, corresponding to the single and double Brillouin frequency shifts, by toggling the optical switch. Under a 980 nm pump power of 600 mw, and a Brillouin pump power of 4 mW and wavelength of 1599.4 nm, up to 16 Stokes signals with a frequency spacing of 0.089 nm and 5 Stokes signals with double spacing of 0.178 nm are generated. A wavelength tunability of 15 nm (1593 nm  -  1608 nm) is realized for both frequency spacings. The fluctuation of Stokes signals for both single and double Brillouin spacing regimes in the proposed setup is less than 1.5 dB throughout a 30 min time span.

Brillouin precursors in Debye media

NASA Astrophysics Data System (ADS)

Macke, Bruno; Ségard, Bernard

2015-05-01

We theoretically study the formation of Brillouin precursors in Debye media. We point out that the precursors are visible only at propagation distances such that the impulse response of the medium is essentially determined by the frequency dependence of its absorption and is practically Gaussian. By simple convolution, we then obtain explicit analytical expressions of the transmitted waves generated by reference incident waves, distinguishing precursor and main signal by a simple examination of the long-time behavior of the overall signal. These expressions are in good agreement with the signals obtained in numerical or real experiments performed on water in the radio-frequency domain and explain in particular some observed shapes of the precursor. Results are obtained for other remarkable incident waves. In addition, we show quite generally that the shape of the Brillouin precursor appearing alone at sufficiently large propagation distance and the law giving its amplitude as a function of this distance do not depend on the precise form of the incident wave but only on its integral properties. The incidence of a static conductivity of the medium is also examined and explicit analytical results are again given in the limit of weak and strong conductivities.

Brillouin Selective Sideband Amplification of Microwave Photonic Signals

NASA Technical Reports Server (NTRS)

Yao, S.

1997-01-01

We introduce a powerful Brillouin selective sideband amplification technique and demonstrate its application for achieving gain in photonix signal up- and down- conversions in microwave photonic systems.

Implementing an Ebola Vaccine Study - Sierra Leone.

PubMed

Widdowson, Marc-Alain; Schrag, Stephanie J; Carter, Rosalind J; Carr, Wendy; Legardy-Williams, Jennifer; Gibson, Laura; Lisk, Durodami R; Jalloh, Mohamed I; Bash-Taqi, Donald A; Kargbo, Samuel A Sheku; Idriss, Ayesha; Deen, Gibrilla F; Russell, James B W; McDonald, Wendi; Albert, Alison P; Basket, Michelle; Callis, Amy; Carter, Victoria M; Ogunsanya, Kelli R Clifton; Gee, Julianne; Pinner, Robert; Mahon, Barbara E; Goldstein, Susan T; Seward, Jane F; Samai, Mohamed; Schuchat, Anne

2016-07-08

In October 2014, the College of Medicine and Allied Health Sciences of the University of Sierra Leone, the Sierra Leone Ministry of Health and Sanitation, and CDC joined the global effort to accelerate assessment and availability of candidate Ebola vaccines and began planning for the Sierra Leone Trial to Introduce a Vaccine against Ebola (STRIVE). STRIVE was an individually randomized controlled phase II/III trial to evaluate efficacy, immunogenicity, and safety of the recombinant vesicular stomatitis virus Ebola vaccine (rVSV-ZEBOV). The study population was health care and frontline workers in select chiefdoms of the five most affected districts in Sierra Leone. Participants were randomized to receive a single intramuscular dose of rVSV-ZEBOV at enrollment or to receive a single intramuscular dose 18-24 weeks after enrollment. All participants were followed up monthly until 6 months after vaccination. Two substudies separately assessed detailed reactogenicity over 1 month and immunogenicity over 12 months. During the 5 months before the trial, STRIVE and partners built a research platform in Sierra Leone comprising participant follow-up sites, cold chain, reliable power supply, and vaccination clinics and hired and trained at least 350 national staff. Wide-ranging community outreach, informational sessions, and messaging were conducted before and during the trial to ensure full communication to the population of the study area regarding procedures and current knowledge about the trial vaccine. During April 9-August 15, 2015, STRIVE enrolled 8,673 participants, of whom 453 and 539 were also enrolled in the safety and immunogenicity substudies, respectively. As of April 28, 2016, no Ebola cases and no vaccine-related serious adverse events, which by regulatory definition include death, life-threatening illness, hospitalization or prolongation of hospitalization, or permanent disability, were reported in the study population. Although STRIVE will not produce an

Ex vivo measurement of postmortem tissue changes in the crystalline lens by Brillouin spectroscopy and confocal reflectance microscopy.

PubMed

Reiss, Stephan; Sperlich, K; Hovakimyan, M; Martius, P; Guthoff, R F; Stolz, H; Stachs, O

2012-08-01

Use of Brillouin spectroscopy in ophthalmology enables noninvasive, spatially resolved determination of the rheological properties of crystalline lens tissue. Furthermore, the Brillouin shift correlates with the protein concentration inside the lens. In vitro measurements on extracted porcine lenses demonstrate that results obtained with Brillouin spectroscopy depend strongly on time after death. The intensity of the Brillouin signal decreases significantly as early as 5 h postmortem. Moreover, the fluctuation of the Brillouin frequency shift inside the lens increases with postmortem time. Images of lens tissue taken with a confocal reflectance microscope between measurements reveal a degenerative aging process. These tissue changes correlate with our results from Brillouin spectroscopy. It is concluded that only in vivo measurements appropriately reflect the rheological properties of the eye lens and its protein concentration.

Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing

PubMed Central

Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A. Ping; Lu, Chao

2016-01-01

We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes. PMID:27999250

Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing.

PubMed

Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A Ping; Lu, Chao

2016-12-16

We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes.

War and deforestation in Sierra Leone

NASA Astrophysics Data System (ADS)

Burgess, Robin; Miguel, Edward; Stanton, Charlotte

2015-09-01

The impact of armed conflict on the environment is of major public policy importance. We use a geographically disaggregated dataset of civil war violence together with satellite imagery of land cover to test whether war facilitated or prevented forest loss in Sierra Leone. The conflict data set allows us to establish where rebel groups were stationed and where battles and attacks occurred. The satellite data enables to us to monitor the change in forest cover (total, primary, and secondary) in all of Sierra Leone’s 151 chiefdoms, between 1990 (prior to the war) and 2000 (just prior to its end). The results suggest that conflict in Sierra Leone acted as a brake on local deforestation: conflict-ridden areas experienced significantly less forest loss relative to their more conflict-free counterparts.

Brillouin Optical Correlation Domain Analysis in Composite Material Beams

PubMed Central

Stern, Yonatan; London, Yosef; Preter, Eyal; Antman, Yair; Diamandi, Hilel Hagai; Silbiger, Maayan; Adler, Gadi; Shalev, Doron; Zadok, Avi

2017-01-01

Structural health monitoring is a critical requirement in many composites. Numerous monitoring strategies rely on measurements of temperature or strain (or both), however these are often restricted to point-sensing or to the coverage of small areas. Spatially-continuous data can be obtained with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K or 20 micro-strain. A portable measurement setup was designed and assembled on the premises of a composite structures manufacturer. The setup was successfully utilized in several structural health monitoring scenarios: (a) monitoring the production and curing of a composite beam over 60 h; (b) estimating the stiffness and Young’s modulus of a composite beam; and (c) distributed strain measurements across the surfaces of a model wing of an unmanned aerial vehicle. The measurements are supported by the predictions of structural analysis calculations. The results illustrate the potential added values of high-resolution, distributed Brillouin sensing in the structural health monitoring of composites. PMID:28974041

Brillouin Optical Correlation Domain Analysis in Composite Material Beams.

PubMed

Stern, Yonatan; London, Yosef; Preter, Eyal; Antman, Yair; Diamandi, Hilel Hagai; Silbiger, Maayan; Adler, Gadi; Levenberg, Eyal; Shalev, Doron; Zadok, Avi

2017-10-02

Structural health monitoring is a critical requirement in many composites. Numerous monitoring strategies rely on measurements of temperature or strain (or both), however these are often restricted to point-sensing or to the coverage of small areas. Spatially-continuous data can be obtained with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K or 20 micro-strain. A portable measurement setup was designed and assembled on the premises of a composite structures manufacturer. The setup was successfully utilized in several structural health monitoring scenarios: (a) monitoring the production and curing of a composite beam over 60 h; (b) estimating the stiffness and Young's modulus of a composite beam; and (c) distributed strain measurements across the surfaces of a model wing of an unmanned aerial vehicle. The measurements are supported by the predictions of structural analysis calculations. The results illustrate the potential added values of high-resolution, distributed Brillouin sensing in the structural health monitoring of composites.

Effect of collisions on amplification of laser beams by Brillouin scattering in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphrey, K. A.; Speirs, D. C.; Trines, R. M. G. M.

2013-10-15

We report on particle in cell simulations of energy transfer between a laser pump beam and a counter-propagating seed beam using the Brillouin scattering process in uniform plasma including collisions. The results presented show that the ion acoustic waves excited through naturally occurring Brillouin scattering of the pump field are preferentially damped without affecting the driven Brillouin scattering process resulting from the beating of the pump and seed fields together. We find that collisions, including the effects of Landau damping, allow for a more efficient transfer of energy between the laser beams, and a significant reduction in the amount ofmore » seed pre-pulse produced.« less

Wavelength dependence of the Brillouin spectral width of boron doped germanosilicate optical fibers.

PubMed

Law, Pi-Cheng; Dragic, Peter D

2010-08-30

Boron co-doped germanosilicate fibers are investigated via the Brillouin light scattering technique using two wavelengths, 1534 nm and 1064 nm. Several fibers are investigated, including four drawn from the same preform but at different draw temperatures. The Stokes' shifts and the Brillouin spectral widths are found to increase with increasing fiber draw temperature. A frequency-squared law has adequately described the wavelength dependence of the Brillouin spectral width of conventional Ge-doped fibers. However, it is found that unlike conventional Ge-doped fibers these fibers do not follow the frequency-squared law. This is explained through a frequency-dependent dynamic viscosity that modifies this law.

Time-domain Brillouin scattering assisted by diffraction gratings

NASA Astrophysics Data System (ADS)

Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi

2018-02-01

Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.

Mechanical characterization at material interfaces through dark field Brillouin microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fiore, Antonio; Scarcelli, Giuliano

2017-02-01

Brillouin microscopy allows high-resolution mapping of the mechanical properties of a sample by measuring the spectra of acoustically induced light scattering therein, and thus has been widely investigated for biomedical application. Measuring the Brillouin spectral shift is challenging when the light is focused onto the interfaces between two materials of different refractive index, because a sizeable portion of the incident light is Fresnel-reflected into the Brillouin spectrometer. To address this need, here, we designed a Brillouin confocal microscope in which the specular reflection at the interface between two materials is physically rejected without significant loss to the Brillouin signal. To achieve this goal, we illuminate the sample with a small-diameter Gaussian beam focused by a high numerical aperture objective lens. In the collection path, the beam reflected from the sample has the same diameter as the incident beam, while the scattered light beam is as large as the clear aperture of the microscope objective. Therefore, using a small blocking filter allows to efficiently reject the reflected light. We calculated the tradeoff between extinction improvement and signal loss when the diameter of the blocking filter is changed. Experimentally, we demonstrated extinction improvement of over 60dB with only 30% signal loss while achieving submicron resolutions. This innovation can be useful for in vivo measurements of the cornea to avoid artifacts in the epithelium and anterior portions of the stroma, as well as to investigate cells cultured on glass coverslips without necessity of index-matching materials.

Stimulated Brillouin scatter in a magnetized ionospheric plasma.

PubMed

Bernhardt, P A; Selcher, C A; Lehmberg, R H; Rodriguez, S P; Thomason, J F; Groves, K M; McCarrick, M J; Frazer, G J

2010-04-23

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f(CI)) or an electrostatic ion cyclotron (EIC) wave just above f(CI) can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.

Detrimental Effect Elimination of Laser Frequency Instability in Brillouin Optical Time Domain Reflectometer by Using Self-Heterodyne Detection

PubMed Central

Li, Yongqian; Li, Xiaojuan; An, Qi; Zhang, Lixin

2017-01-01

A useful method for eliminating the detrimental effect of laser frequency instability on Brillouin signals by employing the self-heterodyne detection of Rayleigh and Brillouin scattering is presented. From the analysis of Brillouin scattering spectra from fibers with different lengths measured by heterodyne detection, the maximum usable pulse width immune to laser frequency instability is obtained to be about 4 µs in a self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR) system using a broad-band laser with low frequency stability. Applying the self-heterodyne detection of Rayleigh and Brillouin scattering in BOTDR system, we successfully demonstrate that the detrimental effect of laser frequency instability on Brillouin signals can be eliminated effectively. Employing the broad-band laser modulated by a 130-ns wide pulse driven electro-optic modulator, the observed maximum errors in temperatures measured by the local heterodyne and self-heterodyne detection BOTDR systems are 7.9 °C and 1.2 °C, respectively. PMID:28335508

Susu Language Manual: Sierra Leone.

ERIC Educational Resources Information Center

Peace Corps, Freetown (Sierra Leone).

A teacher's guide for Susu is designed for Peace Corps volunteer language instruction and geared to the daily language needs of volunteers in Sierra Leone. It contains a section on Susu phonology and 28 lessons on these topics: situation-specific greetings, basic greetings, introducing a friend, the market, travel and getting directions, visiting…

Phase-detected Brillouin optical correlation-domain reflectometry

NASA Astrophysics Data System (ADS)

Mizuno, Yosuke; Hayashi, Neisei; Fukuda, Hideyuki; Nakamura, Kentaro

2018-05-01

Optical fiber sensing techniques based on Brillouin scattering have been extensively studied for structural health monitoring owing to their capability of distributed strain and temperature measurement. Although a higher signal-to-noise ratio (leading to high spatial resolution and high-speed measurement) is generally obtained for two-end-access systems, they reduce the degree of freedom in embedding the sensors into structures, and render the measurement no longer feasible when extremely high loss or breakage occurs at a point of the sensing fiber. To overcome these drawbacks, a one-end-access sensing technique called Brillouin optical correlation-domain reflectometry (BOCDR) has been developed. BOCDR has a high spatial resolution and cost efficiency, but its conventional configuration suffered from relatively low-speed operation. In this paper, we review the recently developed high-speed configurations of BOCDR, including phase-detected BOCDR, with which we demonstrate real-time distributed measurement by tracking a propagating mechanical wave. We also demonstrate breakage detection with a wide strain dynamic range.

Phase-detected Brillouin optical correlation-domain reflectometry

NASA Astrophysics Data System (ADS)

Mizuno, Yosuke; Hayashi, Neisei; Fukuda, Hideyuki; Nakamura, Kentaro

2018-06-01

Optical fiber sensing techniques based on Brillouin scattering have been extensively studied for structural health monitoring owing to their capability of distributed strain and temperature measurement. Although a higher signal-to-noise ratio (leading to high spatial resolution and high-speed measurement) is generally obtained for two-end-access systems, they reduce the degree of freedom in embedding the sensors into structures, and render the measurement no longer feasible when extremely high loss or breakage occurs at a point of the sensing fiber. To overcome these drawbacks, a one-end-access sensing technique called Brillouin optical correlation-domain reflectometry (BOCDR) has been developed. BOCDR has a high spatial resolution and cost efficiency, but its conventional configuration suffered from relatively low-speed operation. In this paper, we review the recently developed high-speed configurations of BOCDR, including phase-detected BOCDR, with which we demonstrate real-time distributed measurement by tracking a propagating mechanical wave. We also demonstrate breakage detection with a wide strain dynamic range.

Brillouin Light Scattering by Magnetic Quasivortices in Cavity Optomagnonics

NASA Astrophysics Data System (ADS)

Osada, A.; Gloppe, A.; Hisatomi, R.; Noguchi, A.; Yamazaki, R.; Nomura, M.; Nakamura, Y.; Usami, K.

2018-03-01

A ferromagnetic sphere can support optical vortices in the form of whispering gallery modes and magnetic quasivortices in the form of magnetostatic modes with nontrivial spin textures. These vortices can be characterized by their orbital angular momenta. We experimentally investigate Brillouin scattering of photons in the whispering gallery modes by magnons in the magnetostatic modes, zeroing in on the exchange of the orbital angular momenta between the optical vortices and magnetic quasivortices. We find that the conservation of the orbital angular momentum results in different nonreciprocal behavior in the Brillouin light scattering. New avenues for chiral optics and optospintronics can be opened up by taking the orbital angular momenta as a new degree of freedom for cavity optomagnonics.

Integrative interactive visualization of crystal structure, band structure, and Brillouin zone

NASA Astrophysics Data System (ADS)

Hanson, Robert; Hinke, Ben; van Koevering, Matthew; Oses, Corey; Toher, Cormac; Hicks, David; Gossett, Eric; Plata Ramos, Jose; Curtarolo, Stefano; Aflow Collaboration

The AFLOW library is an open-access database for high throughput ab-initio calculations that serves as a resource for the dissemination of computational results in the area of materials science. Our project aims to create an interactive web-based visualization of any structure in the AFLOW database that has associate band structure data in a way that allows novel simultaneous exploration of the crystal structure, band structure, and Brillouin zone. Interactivity is obtained using two synchronized JSmol implementations, one for the crystal structure and one for the Brillouin zone, along with a D3-based band-structure diagram produced on the fly from data obtained from the AFLOW database. The current website portal (http://aflowlib.mems.duke.edu/users/jmolers/matt/website) allows interactive access and visualization of crystal structure, Brillouin zone and band structure for more than 55,000 inorganic crystal structures. This work was supported by the US Navy Office of Naval Research through a Broad Area Announcement administered by Duke University.

Stimulated Brillouin Scattering (SBS) Suppression and Long Delivery Fibers at the Multikilowatt Level with Chirped Seed Lasers

DTIC Science & Technology

2017-03-16

stimulated Brillouin scattering [SBS]) due to the large intensity times length product. Efforts to raise the power threshold include 1) reducing the...ARL-TR-7979 ● MAR 2017 US Army Research Laboratory Stimulated Brillouin Scattering (SBS) Suppression and Long Delivery Fibers at...return it to the originator. ARL-TR-7979 ● MAR 2017 US Army Research Laboratory Stimulated Brillouin Scattering (SBS

Scaling up family planning in Sierra Leone: A prospective cost-benefit analysis.

PubMed

Keen, Sarah; Begum, Hashina; Friedman, Howard S; James, Chris D

2017-12-01

Family planning is commonly regarded as a highly cost-effective health intervention with wider social and economic benefits. Yet use of family planning services in Sierra Leone is currently low and 25.0% of married women have an unmet need for contraception. This study aims to estimate the costs and benefits of scaling up family planning in Sierra Leone. Using the OneHealth Tool, two scenarios of scaling up family planning coverage to currently married women in Sierra Leone over 2013-2035 were assessed and compared to a 'no-change' counterfactual. Our costing included direct costs of drugs, supplies and personnel time, programme costs and a share of health facility overhead costs. To monetise the benefits, we projected the cost savings of the government providing five essential social services - primary education, child immunisation, malaria prevention, maternal health services and improved drinking water - in the scale-up scenarios compared to the counterfactual. The total population, estimated at 6.1 million in 2013, is projected to reach 8.3 million by 2035 in the high scenario compared to a counterfactual of 9.6 million. We estimate that by 2035, there will be 1400 fewer maternal deaths and 700 fewer infant deaths in the high scenario compared to the counterfactual. Our modelling suggests that total costs of the family planning programme in Sierra Leone will increase from US$4.2 million in 2013 to US$10.6 million a year by 2035 in the high scenario. For every dollar spent on family planning, Sierra Leone is estimated to save US$2.10 in expenditure on the five selected social sector services over the period. There is a strong investment case for scaling up family planning services in Sierra Leone. The ambitious scale-up scenarios have historical precedent in other sub-Saharan African countries, but the extent to which they will be achieved depends on a commitment from both the government and donors to strengthening Sierra Leone's health system post-Ebola.

Tunable self-seeded multi-wavelength Brillouin-erbium fiber laser based on few-mode fiber filter

NASA Astrophysics Data System (ADS)

Zou, Hui; Ma, Lei; Xiong, Hui; Zhang, Yun-shan; Liu, Chun-xiao

2017-11-01

A tunable self-seeded multi-wavelength Brillouin-erbium fiber laser (BEFL) is proposed and demonstrated based on a few-mode fiber filter (FMFF) with varying temperature. The FMFF configuration is a section of uncoated few-mode fiber (FMF) sandwiched between two up-tapers. As the temperature varies from 25 °C to 125 °C, the transmission spectrum of FMFF moves towards the longer wavelength. The self-excited Brillouin pump is internally achieved by cascaded stimulated Brillouin scattering (SBS) in the single mode fiber (SMF). Then employing the FMFF temperature variation characteristics in the ring cavity fiber laser, the multi-wavelength of the output laser can be tuned, and the tunable range is about 8.0 nm. The generation of up to 15 Brillouin Stokes wavelengths with 16 dB optical signal- to-noise ratio ( OSNR) is realized.

Arbitrary-shaped Brillouin microwave photonic filter by manipulating a directly modulated pump.

PubMed

Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

2017-10-15

We present a cost-effective gigahertz-wide arbitrary-shaped microwave photonic filter based on stimulated Brillouin scattering in fiber using a directly modulated laser (DML). After analyzing the relationship between the spectral power density and the modulation current of the DML, we manage to precisely adjust the optical spectrum of the DML, thereby controlling the Brillouin filter response arbitrarily for the first time, to the best of our knowledge. The filter performance is evaluated by amplifying a 500 Mb/s non-return-to-zero on-off keying signal using a 1 GHz rectangular filter. The comparison between the proposed DML approach and the previous approach adopting a complex IQ modulator shows similar filter flexibility, shape fidelity, and noise performance, proving that the DML-based Brillouin filter technique is a cost-effective and valid solution for microwave photonic applications.

Stimulated Brillouin Scatter in a Magnetized Ionospheric Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernhardt, P. A.; Selcher, C. A.; Lehmberg, R. H.

2010-04-23

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f{sub CI}) or an electrostatic ion cyclotron (EIC) wave just above f{sub CI} can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves aremore » excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.« less

Coronographie interferéntielle pour la mission spatuale DARWIN: expérience de validation en laboratoire

NASA Astrophysics Data System (ADS)

Ollivier, Marc; Mariotti, Jean-Marie; Brunaud, Jacqueline; Michel, Guy; Bouchareine, Patrick; Léger, Alain; Artzner, Guy; Malbet, Fabien; Puget, Pascal; Coudé du Foresto, Vincent; Mennesson, Bertrand

2018-04-01

This paper, "Coronographie interferéntielle pour la mission spatuale DARWIN: expérience de validation en laboratoire," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Optical pulse synthesis using brillouin selective sideband amplification

NASA Technical Reports Server (NTRS)

Yao, X. Steve (Inventor)

2002-01-01

Techniques for producing optical pulses based on Brillouin selective sideband amplification by using a common modulation control signal to modulate both a signal beam to produce multiple sideband signals and a single pump beam to produce multiple pump beams.

Attracting, Recruiting, and Retaining Qualified Faculty at Community Colleges in Sierra Leone

ERIC Educational Resources Information Center

Betts, Gloria

2017-01-01

This case study was designed to explore policies that were in place to attract, recruit, and retain qualified faculty for 4 community colleges in Sierra Leone. The research was necessitated by the apparent inability of Sierra Leone educators to train and retain faculty possessing the required academic credentials. The research questions were…

Leon X-1, the First Chandra Source

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.; Aldcroft, Tom; Cameron, Robert A.; Gandhi, Poshak; Foellmi, Cedric; Elsner, Ronald F.; Patel, Sandeep K.; ODell, Stephen L.

2004-01-01

Here we present an analysis of the first photons detected with the Chandra X-ray Observatory and an identification of the brightest source in the field which we named Leon X-1 to honor the momentous contributions of the Chandra Telescope Scientist, Leon Van Speybroeck. The observation took place immediately following the opening of the last door protecting the X-ray telescope. We discuss the unusual operational conditions as the first extra-terrestrial X-ray photons reflected from the telescope onto the ACIS camera. One bright source was a p parent to the team at the control center and the small collection of photons that appeared on the monitor were sufficient to indicate that the telescope had survived the launch and was approximately in focus, even prior to any checks and subsequent adjustments.

The Met Needs for Pediatric Surgical Conditions in Sierra Leone: Estimating the Gap.

PubMed

Burgos, Carmen Mesas; Bolkan, Håkon Angell; Bash-Taqi, Donald; Hagander, Lars; Von Screeb, Johan

2018-03-01

In low- and middle-income countries, there is a gap between the need for surgery and its equitable provision, and a lack of proxy indicators to estimate this gap. Sierra Leone is a West African country with close to three million children. It is unknown to what extent the surgical needs of these children are met. To describe a nationwide provision of pediatric surgical procedures and to assess pediatric hernia repair as a proxy indicator for the shortage of surgical care in the pediatric population in Sierra Leone. We analyzed results from a nationwide facility survey in Sierra Leone that collected data on surgical procedures from operation and anesthesia logbooks in all facilities performing surgery. We included data on all patients under the age of 16 years undergoing surgery. Primary outcomes were rate and volume of surgical procedures. We calculated the expected number of inguinal hernia in children and estimated the unmet need for hernia repair. In 2012, a total of 2381 pediatric surgical procedures were performed in Sierra Leone. The rate of pediatric surgical procedures was 84 per 100,000 children 0-15 years of age. The most common pediatric surgical procedure was hernia repair (18%), corresponding to a rate of 16 per 100,000 children 0-15 years of age. The estimated unmet need for inguinal hernia repair was 88%. The rate of pediatric surgery in Sierra Leone was very low, and inguinal hernia was the single most common procedure noted among children in Sierra Leone.

Influence of chirp on laser-pulse amplification in Brillouin backscattering schemes

NASA Astrophysics Data System (ADS)

Lehmann, Goetz; Schluck, Friedrich; Spatschek, Karl-Heinz

2015-11-01

Plasma-based amplification of laser pulses is currently discussed as a key component for the next generation of high-intensity laser systems, possibly enabling the generation of ultra-short pulses in the exawatt-zetawatt regime. In these scenarios the energy of a long pump pulse (several ps to ns of duration) is transferred to a short seed pulse via a plasma oscillation. Weakly- and strongly-coupled (sc) Brillouin backscattering have been identified as potential candidates for robust amplification scenarios. With the help of three-wave interaction models, we investigate the influence of a chirp of the pump beam on the seed amplification. We show that chirp can mitigate deleterious spontaneous Raman backscattering of the pump off noise and that at the same time the amplification dynamics due to Brillouin scattering is still intact. For the experimentally very interesting case of sc-Brillouin we find a dependence of the efficiency on the sign of the chirp. Funding provided by project B10 of SFB TR18 of the Deutsche Forschungsgemeinschaft (DFG).

The burden of musculoskeletal disease in Sierra Leone.

PubMed

Elliott, Iain S; Groen, Reinou S; Kamara, Thaim B; Ertl, Allison; Cassidy, Laura D; Kushner, Adam L; Gosselin, Richard A

2015-01-01

Musculoskeletal disease is a major cause of disability in the global burden of disease, yet data regarding the magnitude of this burden in developing countries are lacking. The Surgeons OverSeas Assessment of Surgical Need (SOSAS) survey was designed to measure the incidence and prevalence of surgically treatable conditions, including musculoskeletal conditions, in patients in low- and middle-income countries, and was administered in the West African nation of Sierra Leone in 2012. We attempted to quantify the burden of potentially treatable musculoskeletal conditions in patients in Sierra Leone. A cross-sectional two-stage cluster-based survey was performed in Sierra Leone using the SOSAS. Two individuals from each randomly selected household underwent a verbal head to toe examination. The musculoskeletal-related questions from the SOSAS survey in Sierra Leone were analyzed to determine the prevalence of musculoskeletal problems in the study population. Prevalence is reported as the number of respondents with a musculoskeletal problem now and number of respondents with a musculoskeletal problem during the past year. Respondents had "no need" for care, they "received care", or they faced a barrier that prevented them from receiving care. One thousand eight hundred seventy-five households were targeted, with 1843 undergoing the survey, which yielded 3645 individual respondents. Of the individual respondents, 462 (n=3645; 12.6% of total; 95% CI, 12%-13%) had a traumatic musculoskeletal problem during the past year, and 236 (n=3645; 6% of total; 95% CI, 5%-7%) respondents had a musculoskeletal problem of nontraumatic etiology. Of respondents with either a traumatic or nontraumatic musculoskeletal problem, 359 (n=562; 63.9% of total; 95% CI, 59.5-68.3%) needed care but were unable to receive it with the major barrier reported as financial. Resource allocation decisions in global health are made based on burden of disease data in low- and middle-income countries. The

Interagency technical consultation on improving mortality reporting in Sierra Leone: meeting report

PubMed Central

Asfaw, Yonas; Boateng, Isaac; Calderon, Mauricio; Caleo, Grazia; Conteh, Allan; Conteh, Salifu; Dafae, Foday; Dey, Achintya; Duffy, Nadia; Davies, Daffney; Fatoma, Patrick; Fleming, John; Gogra, Boima; Gorina, Yelena; Grigoryan, Anna; Hersey, Sara; Hoare, Sam; Jabbi, Sonnia-Magba Bu-Buakei; Jambai, Amara; Jasperse, Joseph; Kaiser, Reinhard; Kallon, Gandi; Kamara, Ansumana; Kamara, Fatmata Zara; Kamara, Isata Pamela; Kamara, Wogba; Kandeh, Joseph; Kanu, Mustapha; Kargbo, Mabinty; Kargbo, Samuel; Konie, Richard; Kuyembeh, Simeon; Lansana, Patrick; Mclysaght, Fiona; McCann, Sheena; Nallo, Alhaji Samuka; Ngai, Stephanie; Nichols, Erin; Njuguna, Charles; O-Tipo, Shikanga; Parker, Sulaiman; Rafique, Nuzhat; Redd, John; Samba, Thomas; Souza, Kerry; Tran, Alex; Younge, Chief Mathew Gibao

2017-01-01

By the end of the Ebola epidemic, death reporting in Sierra Leone (SL) became more acceptable amongst local populations, with nearly all deaths being reported to the Ebola hot line alert centers. To continue the positive momentum generated by the epidemic, the Sierra Leone Ministry of Health and Sanitation (MoHS) and the US Centers for Disease Control and Prevention (CDC) organized and conducted the two-day Inter-agency Consultations on Improving Mortality Reporting in Sierra Leone (Consultations). In conjunction with the Consultations, participants were also offered a one-day, in-person training on the major components, characteristics, and uses of a national Civil Registration and Vital Statistics (CRVS) system. To understand processes used by governmental and non-governmental organizations in collection of death data before and during the Ebola epidemic, and to develop recommendations on improving death reporting and CRVS in Sierra Leone. The Inter-agency Consultations were conducted in person over two days in October, 2015. Real-time notes were kept by CDC staff for later abstraction and summarizing. Presenters agreed to share their materials (usually PowerPoint presentations) and approved the summaries. Challenges to implementation and suggestions for improving death reporting were drawn from the presentations and from anonymous suggestions collected at the end of each of three days of the Consultations. The Consultations attracted more than 80 participants from 28 Sierra Leone governmental, business, and other non-governmental organizations. Over the course of 18 presentations, participants presented and discussed the ways deaths were reported before and during the Ebola epidemic and ways in which the CRVS in Sierra Leone might be improved. The presentations made clear the need to improve death reporting in order to improve the health status of Sierra Leone. Many presenters and participants discussed the challenges to improvements, including lack of

Generation of efficient 33 GHz optical combs using cascaded stimulated Brillouin scattering effects in optical fiber

NASA Astrophysics Data System (ADS)

Al-Mansoori, M. H.; Al-Sheriyani, A.; Al-Nassri, S.; Hasoon, F. N.

2017-06-01

In this paper, we demonstrate a multi-wavelength Brillouin-erbium fiber laser (BEFL) with ~33 GHz frequency spacing using cascaded stimulated Brillouin scattering effects in optical fiber. The proposed laser structure exhibits a stable output channel with a tuning range of 19 nm, from 1549 nm to 1568 nm. The number of stable output channels produced is six channels with a triple-Brillouin frequency spacing. The output channels exhibit high output power and high optical signal-to-noise ratios (OSNRs). The laser structure has the potential to be used as a multi-wavelength source for optical communication systems.

Brillouin spectroscopy reveals changes in muscular viscoelasticity in Drosophila POMT mutants

NASA Astrophysics Data System (ADS)

Meng, Zhaokai; Baker, Ryan; Panin, Vladislav M.; Yakovlev, Vladislav V.

2015-03-01

Muscular dystrophy (MD) is a group of muscle diseases that induce weakness in skeletal muscle and cause progressive muscle degeneration. The muscular mechanical properties (i.e., viscoelasticity), however, have not been thoroughly examined before and after MD. On the other hand, Brillouin spectroscopy (BS) provides a non-invasive approach to probing the local sound speed within a small volume. Moreover, recent advances in background-free Brillouin spectroscopy enable investigators to imaging not only transparent samples, but also turbid ones. In this study, we investigated the mechanical properties of muscles while employing Drosophila model of dystroglycanopathies, human congenital muscular dystrophies resulting from abnormal glycosylation of alphadystroglycan. Specifically, we analyzed larval abdominal muscles of Drosophila with mutations in protein Omannosyltransferase (POMT) genes. As a comparison, we have also examined muscular tissues dissected from wildtype Drosophila. The Brillouin spectra were obtained by a background free VIPA (virtually imaged phased array) spectrometer described in the previous report. As a reference, the Raman spectra were also acquired for each test. Our current results indicated that POMT defects cause changes in muscle elasticity, which suggests that muscular dystrophy conditions may be also associated with abnormalities in muscle elastic properties.

Refractive index sensing by Brillouin scattering in side-polished optical fibers.

PubMed

Bernini, Romeo; Persichetti, Gianluca; Catalano, Ester; Zeni, Luigi; Minardo, Aldo

2018-05-15

In this Letter, we demonstrate the possibility to measure the refractive index of a liquid, using the stimulating Brillouin scattering in a 3-cm-long side-polished optical fiber. In addition, we show that by depositing a high-refractive index layer on the polished surface the sensitivity of the Brillouin frequency shift (BFS) can be increased due to a higher penetration of the evanescent field in the outer medium. Experiments show a maximum BFS change of about 11 MHz when varying the refractive index of the external medium from 1 (air) to 1.402, and a BFS sensitivity to refractive index of about 293 MHz/RIU around 1.40.

Stimulated Brillouin scattering materials, experimental design and applications: A review

NASA Astrophysics Data System (ADS)

Bai, Zhenxu; Yuan, Hang; Liu, Zhaohong; Xu, Pengbai; Gao, Qilin; Williams, Robert J.; Kitzler, Ondrej; Mildren, Richard P.; Wang, Yulei; Lu, Zhiwei

2018-01-01

Stimulated Brillouin scattering (SBS), as one type of third-order nonlinear optics effect, is extensively exploited and rapidly developed in the field of lasers and optoelectronics. A large number of theoretical and experimental studies on SBS have been carried out in the past decades. Especially, the exploration of new SBS materials and new types of SBS modulation methods have been engaged simultaneously, as the properties of different materials have great influence on the SBS performance such as generation threshold, Brillouin amplification efficiency, frequency shift, breakdown threshold, etc. This article provides a comprehensive review of the characteristics of different types of SBS materials, SBS applications, experimental design methods, as well as the parameter optimization method, which is expected to provide reference and guidance to SBS related experiments.

Analysis of Security Sector Reform in Post-Conflict Sierra Leone: A Comparison of Current versus Historical Capabilities

DTIC Science & Technology

2010-03-01

6 A. M. Fitz -Gerald, Security Sector Reform in Sierra Leone. Shrivenham, GFN-SSR. 8–10. Osman Gbla...34Security Sector Reform: Bringing the Private in.", 1– 23; Peter Albrecht and Paul Jackson, eds. Security System Transformation in Sierra Leone, 1997–2007...veterans.38 33 John R. Cartwright, Political leadership in Sierra Leone (Toronto: University of

The Performance Analysis of Distributed Brillouin Corrosion Sensors for Steel Reinforced Concrete Structures

PubMed Central

Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

2014-01-01

The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage. PMID:24379048

The performance analysis of distributed Brillouin corrosion sensors for steel reinforced concrete structures.

PubMed

Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

2013-12-27

The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage.

Localization of the interband transitions in the bulk of the Brillouin zone of III–V compound crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, V. V., E-mail: sobolev@uni.udm.ru; Perevoshchikov, D. A.

2016-05-15

The localization of the transitions in the bulk of the Brillouin zone that form the main structures in the spectra of the imaginary part of the permittivity in the range up to ~7 eV for III–V semiconductors (AlSb, GaSb, InSb, and InAs) is determined using electron density functional theory. It is established that intense transitions occur not only in the vicinity of the high-symmetry axes of the Brillouin zone, but also in some specific large volumes of the irreducible part of the Brillouin zone.

Non-Governmental Organizations in Africa: The Leonenet Street Children Project in Sierra Leone

ERIC Educational Resources Information Center

Hinton, Samuel

2005-01-01

The purpose of this paper is to provide snapshots of observations, interventions, and processes in the day to day working of a child charity in Sierra Leone. There were 114 local and 49 overseas funded Non Governmental Organizations (NGOs) in Sierra Leone in 2002. The Leonenet Street Children Project was founded in 1996 by the membership of the…

Assessment of Anemia Knowledge, Attitudes and Behaviors among Pregnant Women in Sierra Leone

ERIC Educational Resources Information Center

M'Cormack, Fredanna A. D.; Drolet, Judy C.

2012-01-01

Introduction: Iron deficiency anemia prevalence of pregnant Sierra Leone women currently is reported to be 59.7%. Anemia is considered to be a direct cause of 3-7% of maternal deaths and an indirect cause of 20-40% of maternal deaths. This study explores knowledge, attitudes, and behaviors of urban pregnant Sierra Leone women regarding anemia.…

Health complications of female genital mutilation in Sierra Leone

PubMed Central

Bjälkander, Owolabi; Bangura, Laurel; Leigh, Bailah; Berggren, Vanja; Bergström, Staffan; Almroth, Lars

2012-01-01

Sierra Leone has one of the highest rates of female genital mutilation (FGM) in the world, and yet little is known about the health consequences of the practice. Purpose To explore whether and what kind of FGM-related health complications girls and women in Sierra Leone experience, and to elucidate their health care-seeking behaviors. Patients and methods A feasibility study was conducted to test and refine questionnaires and methods used for this study. Thereafter, a cross-section of girls and women (n = 258) attending antenatal care and Well Women Clinics in Bo Town, Bo District, in the southern region and in Makeni Town, Bombali District, in the northern region of Sierra Leone were randomly selected. Participants answered interview-administrated pretested structured questionnaires with open- ended-questions, administrated by trained female personnel. Results All respondents had undergone FGM, most between 10 and 14 years of age. Complications were reported by 218 respondents (84.5%), the most common ones being excessive bleeding, delay in or incomplete healing, and tenderness. Fever was significantly more often reported by girls who had undergone FGM before 10 years of age compared with those who had undergone the procedure later. Out of those who reported complications, 187 (85.8%) sought treatment, with 89 of them visiting a traditional healer, 75 a Sowei (traditional circumciser), and 16 a health professional. Conclusion The high prevalence rate of FGM and the proportion of medical complications show that FGM is a matter for public health concern in Sierra Leone. Girls who undergo FGM before 10 years of age seem to be more vulnerable to serious complications than those who are older at the time of FGM. It is important that health care personnel are aware of, and look for possible complications from FGM, and encourage girls and women to seek medical care for their problems. PMID:22870046

Colour cyclic code for Brillouin distributed sensors

NASA Astrophysics Data System (ADS)

Le Floch, Sébastien; Sauser, Florian; Llera, Miguel; Rochat, Etienne

2015-09-01

For the first time, a colour cyclic coding (CCC) is theoretically and experimentally demonstrated for Brillouin optical time-domain analysis (BOTDA) distributed sensors. Compared to traditional intensity-modulated cyclic codes, the code presents an additional gain of √2 while keeping the same number of sequences as for a colour coding. A comparison with a standard BOTDA sensor is realized and validates the theoretical coding gain.

Initiatives for Sustainable Community Development in Sierra Leone.

ERIC Educational Resources Information Center

Kamara, John M.; Kargbo, Stephen B.

1999-01-01

In Sierra Leone, two church-sponsored programs are focused on sustainable development. The Wesleyan Development Education and Awareness Programme trains people to initiate community projects. Women's Loan Scheme encourages development of small-scale enterprises. (SK)

Identity with Jesus Christ: the case of Leon Gabor.

PubMed

Capps, Donald

2010-12-01

From July 1, 1959 to August 15, 1961, Milton Rokeach studied three male patients at Ypsilanti State Hospital who believed that they were Jesus Christ. They met regularly together with Rokeach and his research staff, a procedure designed to challenge their delusional systems. He believed that Leon Gabor, the youngest of the three, would be the most likely to abandon his delusional beliefs. Instead, Leon met the challenges that the procedure posed by creative elaborations of his delusional system, especially through the adoption of a new name that gave the initial appearance of the abandonment of his Christ identity but in fact drew on aspects of the real Jesus Christ's identity that were missing from his earlier self-representation.

Undiagnosed Acute Viral Febrile Illnesses, Sierra Leone

PubMed Central

Rossi, Cynthia A.; Khan, Sheik H.; Goba, Augustine; Fair, Joseph N.

2014-01-01

Sierra Leone in West Africa is in a Lassa fever–hyperendemic region that also includes Guinea and Liberia. Each year, suspected Lassa fever cases result in submission of ≈500–700 samples to the Kenema Government Hospital Lassa Diagnostic Laboratory in eastern Sierra Leone. Generally only 30%–40% of samples tested are positive for Lassa virus (LASV) antigen and/or LASV-specific IgM; thus, 60%–70% of these patients have acute diseases of unknown origin. To investigate what other arthropod-borne and hemorrhagic fever viral diseases might cause serious illness in this region and mimic Lassa fever, we tested patient serum samples that were negative for malaria parasites and LASV. Using IgM-capture ELISAs, we evaluated samples for antibodies to arthropod-borne and other hemorrhagic fever viruses. Approximately 25% of LASV-negative patients had IgM to dengue, West Nile, yellow fever, Rift Valley fever, chikungunya, Ebola, and Marburg viruses but not to Crimean-Congo hemorrhagic fever virus. PMID:24959946

Cyclic coding for Brillouin optical time-domain analyzers using probe dithering.

PubMed

Iribas, Haritz; Loayssa, Alayn; Sauser, Florian; Llera, Miguel; Le Floch, Sébastien

2017-04-17

We study the performance limits of mono-color cyclic coding applied to Brillouin optical time-domain analysis (BOTDA) sensors that use probe wave dithering. BOTDA analyzers with dithering of the probe use a dual-probe-sideband setup in which an optical frequency modulation of the probe waves along the fiber is introduced. This avoids non-local effects while keeping the Brillouin threshold at its highest level, thus preventing the spontaneous Brillouin scattering from generating noise in the deployed sensing fiber. In these conditions, it is possible to introduce an unprecedented high probe power into the sensing fiber, which leads to an enhancement of the signal-to-noise ratio (SNR) and consequently to a performance improvement of the analyzer. The addition of cyclic coding in these set-ups can further increase the SNR and accordingly enhance the performance. However, this unprecedented probe power levels that can be employed result in the appearance of detrimental effects in the measurement that had not previously been observed in other BOTDA set-ups. In this work, we analyze the distortion in the decoding process and the errors in the measurement that this distortion causes, due to three factors: the power difference of the successive pulses of a code sequence, the appearance of first-order non-local effects and the non-linear amplification of the probe wave that results when using mono-color cyclic coding of the pump pulses. We apply the results of this study to demonstrate the performance enhancement that can be achieved in a long-range dithered dual-probe BOTDA. A 164-km fiber-loop is measured with 1-m spatial resolution, obtaining 3-MHz Brillouin frequency shift measurement precision at the worst contrast location. To the best of our knowledge, this is the longest sensing distance achieved with a BOTDA sensor using mono-color cyclic coding.

Landsat-Derived Estimates of Mangrove Extents in the Sierra Leone Coastal Landscape Complex during 1990-2016.

PubMed

Mondal, Pinki; Trzaska, Sylwia; de Sherbinin, Alex

2017-12-21

This study provides the first assessment of decadal changes in mangrove extents in Sierra Leone. While significant advances have been made in mangrove mapping using remote sensing, no study has documented long-term changes in mangrove extents in Sierra Leone-one of the most vulnerable countries in West Africa. Such understanding is critical for devising regional management strategies that can support local livelihoods. We utilize multi-date Landsat data and cloud computational techniques to quantify spatiotemporal changes in land cover, with focus on mangrove ecosystems, for 1990-2016 along the coast of Sierra Leone. We specifically focus on four estuaries-Scarcies, Sierra Leone, Yawri Bay, and Sherbro. We relied on the k-means approach for an unsupervised classification, and validated the classified map from 2016 using ground truth data collected from Sentinel-2 and high-resolution images and during field research (accuracy: 95%). Our findings indicate that the Scarcies river estuary witnessed the greatest mangrove loss since 1990 (45%), while the Sierra Leone river estuary experienced mangrove gain over the last 26 years (22%). Overall, the Sierra Leone coast lost 25% of its mangroves between 1990 and 2016, with the lowest coverage in 2000, during the period of civil war (1991-2002). However, natural mangrove dynamics, as supported by field observations, indicate the potential for regeneration and sustainability under carefully constructed management strategies.

Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

NASA Astrophysics Data System (ADS)

Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

2016-03-01

Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

Tendency of a rotating electron plasma to approach the Brillouin limit

DOE PAGES

Gueroult, Renaud; Fruchtman, Amnon; Fisch, Nathaniel J.

2013-07-24

In this study, a neutral plasma is considered to be immersed in an axial magnetic field together with a radial electric field. If the electrons are magnetized, but the ions are not magnetized, then the electrons will rotate but the ions will not rotate, leading to current generation. The currents, in turn, weaken the axial magnetic field, leading to an increase in the rotation frequency of the slow Brillouin mode. This produces a positive feedback effect, further weakening the magnetic field. The operating point thus tends to drift towards the Brillouin limit, possibly finding stability only in proximity to themore » limit itself. An example of this effect might be the cylindrical Hall thruster configuration.« less

Extraction of a single Stokes line from a Brillouin fibre laser using a silicon oxynitride microring filter

NASA Astrophysics Data System (ADS)

Zulkifli, M. Z.; Chong, W. Y.; Melloni, A.; Morichetti, F.; Harun, S. W.; Ahmad, H.

2013-09-01

Extraction of a single channel Brillouin Stokes line generated by pumping a length of single mode fibre is demonstrated using a silicon oxynitride microring resonator. The high Q-factor microring resonator has a steep slope transmission profile with an extinction ratio of 20 dB and a free spectral range of 0.4 nm. Experimental results show that extraction of a single Brillouin Stokes line can be achieved with a side mode suppression ratio of more than 12 dB. Additionally, Brillouin Stokes line selection can be achieved by controlling the microring resonance wavelength by thermal tuning.

Interviews with Exemplary Teachers: Leon F. Litwack.

ERIC Educational Resources Information Center

Rosenzweig, Roy

2001-01-01

Presents an interview with Leon F. Litwack, a professor of U.S. history at the University of California, Berkeley. Covers topics such as what led him to teaching history, his lectures at Berkeley, themes covered in his U.S. history surveys, and his perception of good teaching. (CMK)

South African Ebola diagnostic response in Sierra Leone: A modular high biosafety field laboratory

PubMed Central

Jansen van Vuren, Petrus; Meier, Gunther H.; le Roux, Chantel; Conteh, Ousman S.; Kemp, Alan; Fourie, Cardia; Naidoo, Prabha; Naicker, Serisha; Ohaebosim, Phumza; Storm, Nadia; Hellferscee, Orienka; Ming Sun, Lisa K.; Mogodi, Busisiwe; Prabdial-Sing, Nishi; du Plessis, Desiree; Greyling, Deidre; Loubser, Shayne; Goosen, Mark; McCulloch, Stewart D.; Scott, Terence P.; Moerdyk, Alexandra; Dlamini, Wesley; Konneh, Kelfala; Kamara, Idrissa L.; Sowa, Dauda; Sorie, Samuel; Kargbo, Brima; Madhi, Shabir A.

2017-01-01

Background In August 2014, the National Institute for Communicable Diseases (NICD) in South Africa established a modular high-biosafety field Ebola diagnostic laboratory (SA FEDL) near Freetown, Sierra Leone in response to the rapidly increasing number of Ebola virus disease (EVD) cases. Methods and findings The SA FEDL operated in the Western Area of Sierra Leone, which remained a “hotspot” of the EVD epidemic for months. The FEDL was the only diagnostic capacity available to respond to the overwhelming demand for rapid EVD laboratory diagnosis for several weeks in the initial stages of the EVD crisis in the capital of Sierra Leone. Furthermore, the NICD set out to establish local capacity amongst Sierra Leonean nationals in all aspects of the FEDL functions from the outset. This led to the successful hand-over of the FEDL to the Sierra Leone Ministry of Health and Sanitation in March 2015. Between 25 August 2014 and 22 June 2016, the laboratory tested 11,250 specimens mostly from the Western Urban and Western Rural regions of Sierra Leone, of which 2,379 (21.14%) tested positive for Ebola virus RNA. Conclusions The bio-safety standards and the portability of the SA FEDL, offered a cost-effective and practical alternative for the rapid deployment of a field-operated high biocontainment facility. The SA FEDL teams demonstrated that it is highly beneficial to train the national staff in the course of formidable disease outbreak and accomplished their full integration into all operational and diagnostic aspects of the laboratory. This initiative contributed to the international efforts in bringing the EVD outbreak under control in Sierra Leone, as well as capacitating local African scientists and technologists to respond to diagnostic needs that might be required in future outbreaks of highly contagious pathogens. PMID:28628619

South African Ebola diagnostic response in Sierra Leone: A modular high biosafety field laboratory.

PubMed

Paweska, Janusz T; Jansen van Vuren, Petrus; Meier, Gunther H; le Roux, Chantel; Conteh, Ousman S; Kemp, Alan; Fourie, Cardia; Naidoo, Prabha; Naicker, Serisha; Ohaebosim, Phumza; Storm, Nadia; Hellferscee, Orienka; Ming Sun, Lisa K; Mogodi, Busisiwe; Prabdial-Sing, Nishi; du Plessis, Desiree; Greyling, Deidre; Loubser, Shayne; Goosen, Mark; McCulloch, Stewart D; Scott, Terence P; Moerdyk, Alexandra; Dlamini, Wesley; Konneh, Kelfala; Kamara, Idrissa L; Sowa, Dauda; Sorie, Samuel; Kargbo, Brima; Madhi, Shabir A

2017-06-01

In August 2014, the National Institute for Communicable Diseases (NICD) in South Africa established a modular high-biosafety field Ebola diagnostic laboratory (SA FEDL) near Freetown, Sierra Leone in response to the rapidly increasing number of Ebola virus disease (EVD) cases. The SA FEDL operated in the Western Area of Sierra Leone, which remained a "hotspot" of the EVD epidemic for months. The FEDL was the only diagnostic capacity available to respond to the overwhelming demand for rapid EVD laboratory diagnosis for several weeks in the initial stages of the EVD crisis in the capital of Sierra Leone. Furthermore, the NICD set out to establish local capacity amongst Sierra Leonean nationals in all aspects of the FEDL functions from the outset. This led to the successful hand-over of the FEDL to the Sierra Leone Ministry of Health and Sanitation in March 2015. Between 25 August 2014 and 22 June 2016, the laboratory tested 11,250 specimens mostly from the Western Urban and Western Rural regions of Sierra Leone, of which 2,379 (21.14%) tested positive for Ebola virus RNA. The bio-safety standards and the portability of the SA FEDL, offered a cost-effective and practical alternative for the rapid deployment of a field-operated high biocontainment facility. The SA FEDL teams demonstrated that it is highly beneficial to train the national staff in the course of formidable disease outbreak and accomplished their full integration into all operational and diagnostic aspects of the laboratory. This initiative contributed to the international efforts in bringing the EVD outbreak under control in Sierra Leone, as well as capacitating local African scientists and technologists to respond to diagnostic needs that might be required in future outbreaks of highly contagious pathogens.

Individual and community perceptions of surgical care in Sierra Leone.

PubMed

Groen, Reinou S; Sriram, Veena M; Kamara, Thaim B; Kushner, Adam L; Blok, Lucie

2014-01-01

To determine themes and beliefs that influence health-seeking behaviour and barriers to accessing surgical care. In January 2012 in Western Area Province of Sierra Leone, six Focus Group Discussions (FGDs) were conducted. The FDGs consisted of three male only and three female only groups in an urban, a slum and a rural setting. Researchers investigated a wide range of topics including definitions of surgery, types of surgical procedures, trust, quality of care, human resources, post-operative care, permission-seeking and traditional beliefs. Although many individual beliefs were expressed, common fears were as follows: becoming half human after surgery; complications from procedures; stigma from having a scar; and financial burdens resulting from the cost of care. Participants also expressed concern about the quality of the care available in Sierra Leone. The concept of being half human after surgery, previously not documented in the literature, is noteworthy and should be explored more fully. Qualitative research in other parts of Sierra Leone and other LMICs into beliefs of the local population could improve programmes for access and delivery of surgical care. © 2013 John Wiley & Sons Ltd.

Areas Contributing Recharge to Wells in the Tafuna-Leone Plain, Tutuila, American Samoa

USGS Publications Warehouse

Izuka, Scot K.; Perreault, Jeff A.; Presley, Todd K.

2007-01-01

To address the concerns about the potential for contamination of drinking-water wells in the Tafuna-Leone Plain, Tutuila, American Samoa, a numerical ground-water flow model was developed and used to delineate areas contributing recharge to the wells (ACRWs). Surveys and analyses were conducted to obtain or compile certain essential hydrogeologic information needed for the model, such as groundwater production statistics, ground-water levels under current production, and an assessment of the distribution of groundwater recharge. The ground-water surveys indicate that total production from all wells in the Tafuna-Leone Plain between 1985 and 2005 averaged 6.1 Mgal/d and showed a gradual increase. A synoptic survey indicates that current water levels in the Tafuna-Leone Plain are highest near its inland boundary, decrease toward the coast, and are slightly depressed in high-production well fields. Ground-water levels showed little effect from the increased production because hydraulic conductivites are high and withdrawal is small relative to recharge. Analysis of ground-water recharge using a soil water-budget analysis indicates that the Tafuna-Leone Plain and adjacent areas receive about 280 Mgal/d of water from rainfall, of which 24 percent runs off to the ocean, 26 percent is removed by evapotranspiration, and 50 percent goes to ground-water recharge. Ground-water recharge per unit area is generally higher at the mountain crests than at the coast, but the highest recharge per unit area is in the mountain-front recharge zone at the juncture between the Tafuna-Leone Plain and the adjacent mountains. Surface water from the mountains also contributes to ground-water recharge in the eastern Tafuna-Leone Plain, in a process analogous to mountain-front recharge described in arid areas. Analysis of stream-gage data indicates that in the mountains of Tutuila, ground water discharges and contributes substantially to the total flow of the streams. In contrast, multiple

What is the Brillouin zone of an anisotropic photonic crystal?

NASA Astrophysics Data System (ADS)

Sivarajah, P.; Maznev, A. A.; Ofori-Okai, B. K.; Nelson, K. A.

2016-02-01

The concept of the Brillouin zone (BZ) in relation to a photonic crystal fabricated in an optically anisotropic material is explored both experimentally and theoretically. In experiment we used femtosecond laser pulses to excite THz polaritons and image their propagation in lithium niobate and lithium tantalate photonic crystal (PhC) slabs. We directly measured the dispersion relation inside PhCs and observed that the lowest band gap expected to form at the BZ boundary forms inside the BZ in the anisotropic lithium niobate PhC. Our analysis shows that in an anisotropic material the BZ—defined as the Wigner-Seitz cell in the reciprocal lattice—is no longer bounded by Bragg planes and thus does not conform to the original definition of the BZ by Brillouin. We construct an alternative Brillouin zone defined by Bragg planes and show its utility in identifying features of the dispersion bands. We show that for an anisotropic two-dimensional PhC without dispersion, the Bragg plane BZ can be constructed by applying the Wigner-Seitz method to a stretched or compressed reciprocal lattice. We also show that in the presence of the dispersion in the underlying material or in a slab waveguide, the Bragg planes are generally represented by curved surfaces rather than planes. The concept of constructing a BZ with Bragg planes should prove useful in understanding the formation of dispersion bands in anisotropic PhCs and in selectively tailoring their optical properties.

Long-term stability enhancement of Brillouin measurement in polymer optical fibers using amorphous fluoropolymer

NASA Astrophysics Data System (ADS)

Matsutani, Natsuki; Lee, Heeyoung; Mizuno, Yosuke; Nakamura, Kentaro

2018-01-01

For Brillouin-sensing applications, we develop a method for mitigating the Fresnel reflection at the perfluorinated-polymer-optical-fiber ends by covering them with an amorphous fluoropolymer (CYTOP, fiber core material) dissolved in a volatile solvent. Unlike the conventional method using water, even after solvent evaporation, the CYTOP layer remains, resulting in long-term Fresnel reduction. In addition, the high viscosity of the CYTOP solution is a practical advantage. The effectiveness of this method is experimentally proved by Brillouin measurement.

Enhanced performance for differential detection in coherent Brillouin optical time-domain analysis sensors

NASA Astrophysics Data System (ADS)

Shao, Liyang; Zhang, Yunpeng; Li, Zonglei; Zhang, Zhiyong; Zou, Xihua; Luo, Bin; Pan, Wei; Yan, Lianshan

2016-11-01

Logarithmic detectors (LogDs) have been used in coherent Brillouin optical time-domain analysis (BOTDA) sensors to reduce the effect of phase fluctuation, demodulation complexities, and measurement time. However, because of the inherent properties of LogDs, a DC component at the level of hundreds of millivolts that prohibits high-gain signal amplification (SA) could be generated, resulting in unacceptable data acquisition (DAQ) inaccuracies and decoding errors in the process of prototype integration. By generating a reference light at a level similar to the probe light, differential detection can be applied to remove the DC component automatically using a differential amplifier before the DAQ process. Therefore, high-gain SA can be employed to reduce quantization errors. The signal-to-noise ratio of the weak Brillouin gain signal is improved from ˜11.5 to ˜21.8 dB. A BOTDA prototype is implemented based on the proposed scheme. The experimental results show that the measurement accuracy of the Brillouin frequency shift (BFS) is improved from ±1.9 to ±0.8 MHz at the end of a 40-km sensing fiber.

Simplified Modeling of Steady-State and Transient Brillouin Gain in Magnetoactive Non-Centrosymmetric Semiconductors

NASA Astrophysics Data System (ADS)

Singh, M.; Aghamkar, P.; Sen, P. K.

With the aid of a hydrodynamic model of semiconductor-plasmas, a detailed analytical investigation is made to study both the steady-state and the transient Brillouin gain in magnetized non-centrosymmetric III-V semiconductors arising from the nonlinear interaction of an intense pump beam with the internally-generated acoustic wave, due to piezoelectric and electrostrictive properties of the crystal. Using the fact that the origin of coherent Brillouin scattering (CBS) lies in the third-order (Brillouin) susceptibility of the medium, we obtained an expression of the gain coefficient of backward Stokes mode in steady-state and transient regimes and studied the dependence of piezoelectricity, magnetic field and pump pulse duration on its growth rate. The threshold-pump intensity and optimum pulse duration for the onset of transient CBS are estimated. The piezoelectricity and externally-applied magnetic field substantially enhances the transient CBS gain coefficient in III-V semiconductors which can be of great use in the compression of scattered pulses.

Brillouin Amplification--A Powerful New Scheme for Microwave Photonic Communications

NASA Technical Reports Server (NTRS)

Yao, S.; Maleki, L.

1997-01-01

We introduce the Brillouin selective sideband amplification technique and demonstrate many important applications of this technique in photonic microwave systems, including efficient phase modulation to amplitude modulation conversion, photonic frequency multiplication, photonic signal mixing with gain, and frequency multiplied signal up conversion.

Dependence of the Brillouin gain spectrum on linear strain distribution for optical time-domain reflectometer-type strain sensors

NASA Astrophysics Data System (ADS)

Naruse, Hiroshi; Tateda, Mitsuhiro; Ohno, Hiroshige; Shimada, Akiyoshi

2002-12-01

We theoretically derive the shape of the Brillouin gain spectrum, that is, the Brillouin backscattered-light power spectrum, produced in an optical fiber under conditions of a strain distribution that changes linearly with a constant slope. The modeled measurement system is an optical time-domain reflectometer-type strain sensor system. The linear strain distribution is one of the fundamental distributions and is produced in, for example, a beam to which a concentrated load is applied. By analyzing a function that expresses the shape of the derived Brillouin gain spectrum, we show that the strain calculated from the frequency at which the spectrum has a peak value coincides with that at the center of the effective pulsed light. In addition, the peak value and the full width at half-maximum of the Brillouin gain spectrum are both influenced by the strain difference between the two ends of the effective pulse. We investigate this influence in detail and obtain the relationship between strain difference and strain measurement error.

Development of a Brillouin scattering based distributed fibre optic strain sensor

NASA Astrophysics Data System (ADS)

Brown, Anthony Wayne

2001-07-01

The parameters of the Brillouin spectrum of an optical fibre depend upon the strain and temperature conditions of the fibre. As a result, fibre optic distributed sensors based on Brillouin scattering can measure strain and temperature in arbitrary regions of a sensing fibre. In the past, such sensors have often been demonstrated under laboratory conditions, demonstrating the principle of operation. Although some field tests of temperature sensing have been reported, the actual deployment of such sensors in the field for strain measurements has been limited by poor spatial resolution (typically 1 m or more) and poor strain accuracy (+/-100 muepsilon). Also, cross-sensitivity of the Brillouin spectrum to temperature further reduces the accuracy of strain measurement while long acquisition times hinders field use. The high level of user knowledge and lack of automation required to operate the equipment is another limiting factor of the only commercially available unit. The potential benefits of distributed measurements are great for instrumentation of civil structures provided that the above limitations are overcome. However, before this system is used with confidence by practitioners, it is essential that it can be effectively operated in field conditions. In light of this, the fibre optics group at the University of New Brunswick has been developing an automated system for field measurement of strain in civil structures, particularly in reinforced concrete. The development of the sensing system hardware and software was the main focus of this thesis. This has been made possible, in part, by observation of the Brillouin spectrum for the case of using very short light pulses (<10 ns). The end product of the development is a sensor with a spatial resolution that has been improved to 100 mm. Measurement techniques that improve system performance to measure strain to an accuracy of 10 muepsilon; and allow the simultaneous measurement of strain and temperature to an

Leon Foucault: His Life, Times and Achievements

ERIC Educational Resources Information Center

Aczel, Amir D.

2004-01-01

Leon Foucault's dramatic demonstration of the rotation of the Earth using a freely-rotating pendulum in 1850 shocked the world of science. Scientists were stunned that such a simple proof of our planet's rotation had to wait so long to be developed. Foucault's public demonstration, which was repeated at many locations around the world, put an end…

Residual strain sensor using Al-packaged optical fiber and Brillouin optical correlation domain analysis.

PubMed

Choi, Bo-Hun; Kwon, Il-Bum

2015-03-09

We propose a distributed residual strain sensor that uses an Al-packaged optical fiber for the first time. The residual strain which causes Brillouin frequency shifts in the optical fiber was measured using Brillouin optical correlation domain analysis with 2 cm spatial resolution. We quantified the Brillouin frequency shifts in the Al-packaged optical fiber by the tensile stress and compared them for a varying number of Al layers in the optical fiber. The Brillouin frequency shift of an optical fiber with one Al layer had a slope of 0.038 MHz/με with respect to tensile stress, which corresponds to 78% of that for an optical fiber without Al layers. After removal of the stress, 87% of the strain remained as residual strain. When different tensile stresses were randomly applied, the strain caused by the highest stress was the only one detected as residual strain. The residual strain was repeatedly measured for a time span of nine months for the purpose of reliability testing, and there was no change in the strain except for a 4% reduction, which is within the error tolerance of the experiment. A composite material plate equipped with our proposed Al-packaged optical fiber sensor was hammered for impact experiment and the residual strain in the plate was successfully detected. We suggest that the Al-packaged optical fiber can be adapted as a distributed strain sensor for smart structures, including aerospace structures.

6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL RELIEF OF TRANSPORTATION BY AUTOMOBILE - Calvert Street Bridge, Spanning Rock Creek & Potomac Parkway, Washington, District of Columbia, DC

Comparison of surgical care deficiencies between US civil war hospitals and present-day hospitals in Sierra Leone.

PubMed

Crompton, Joseph; Kingham, T Peter; Kamara, T B; Brennan, Murray F; Kushner, Adam L

2010-08-01

Surgery is rapidly becoming a part of public health initiatives in developing countries. In collaboration with the Sierra Leone Ministry of Health and Sanitation, a team of local surgeons and surgeons from the organization Surgeons OverSeas (SOS) used the WHO Tool for Situational Analysis to Assess Emergency Surgical Care to quantify surgical capacity in Sierra Leone. These data were then compared to data collected from the Medical and Surgical History of the Civil War, a work documenting surgical care and hospitals during the US Civil War. There are 0.2 government hospital surgeons/100,000 people in Sierra Leone compared to 300 surgeons/100,000 soldiers in the Union Army. In Sierra Leone it is rare to have running water, fuel, anesthesia, and reliable X-rays. In comparison, US Civil War hospitals had reliable running water, fuel, and anesthesia. It is rare to manage open fractures, limb dislocations, amputations, and conditions requiring chest tubes in Sierra Leone, while these procedures were commonly employed in US Civil War hospitals. Government hospitals in present day Sierra Leone lack the infrastructure, personnel, supplies, and equipment to adequately provide emergency and essential surgical care. In a comparison of present day Sierra Leonean and US Civil War hospitals, the US Civil War facilities are equivalent and in many ways superior. It is hoped that such a comparison will aid advocacy efforts so that greater resources are devoted to improving emergency and essential surgical care in low- and middle-income countries.

Brillouin Scattering from Opaque Semiconducting Alloys and Thin Films.

NASA Astrophysics Data System (ADS)

Krabach, Timothy Norbert

Brillouin scattering spectra were measured in MBE grown single crystal films of Al_{ rm x}Ga_{rm 1 - x}As alloys and Al_{ rm x}Ga_{rm 1 - x}As-GaAs superlattices on GaAs substrates, and GaAs films grown on miscut Si substrates. To detect the Brillouin shifted light against the strong elastic background present in opaque materials, a tandem multipass Fabry-Perot system was designed and constructed, providing high resolution and contrast. Scattering from both surface and bulk acoustic waves were used to derive information on the elastic and dielectric constants of Al_{rm x}Ga_{rm 1 - x} As alloys. The surface acoustic wave velocities along the (100) and (110) axes were measured for a number of aluminum concentrations. In samples that were transparent to the exciting laser frequency, a leaky surface longitudinal wave was also observed. By fitting to this data, the elastic constants as a function of alloy concentration were found to be c_{11} = 11.88 + 0.05x, c_{12} = 5.38 + 1.6x, and c_{44} = 5.95 - .8x (times 10^{10} dyn/cm ^2). Scattering from bulk acoustic waves was used to measure the complex index of refraction. The results agree very closely with previous ellipsometric data. Spectra were taken on two superlattices and compared to an alloy of the same average aluminum concentration. No differences were seen in the acoustic velocities or the index of refraction. Brillouin spectra taken of GaAs films on Si exhibited peaks due to acoustic waves trapped in the film. The dispersion curves of these modes as a function of wavevector were fitted by using the bulk elastic constants of GaAs and Si. The good fit obtained, and the narrowness of the peaks, are corroborating evidence of the high crystalline quality of these films.

KrF laser amplifier with phase-conjugate Brillouin retroreflectors.

PubMed

Gower, M C

1982-09-01

We have demonstrated the use of phase-conjugate stimulated Brillouin scattering mirrors to produce high-quality, short-pulse KrF laser beams from angular multiplexed and regenerative amplifiers. The mirror was also shown to isolate systems optically from amplifier spontaneous emission. Automatic alignment of targets using this mirror as a retroreflector was also demonstrated.

Nationally representative household survey of surgery and mortality in Sierra Leone.

PubMed

Kwon, Steve; Groen, Reinou S; Kamara, Thaim B; Cassidy, Laura D; Samai, Mohamed; Yambasu, Sahr E; Kushner, Adam L

2013-08-01

There is limited evidence to characterize the burden of unmet need of surgical diseases in low- and middle-income countries. The purpose of this study was to determine rate of deaths attributable to a surgical condition and reasons for not seeking surgical care in Sierra Leone. The Surgeons OverSeas Assessment of Surgical Need (SOSAS) is a survey tool developed collaboratively to be used for cross-sectional data collection of the prevalence of surgical conditions in any country. A population-weighted cluster-sample household survey was conducted throughout Sierra Leone in 2012 using the SOSAS survey tool. Total of 1,840 households (11,870 individuals) were sampled, yielding a 98.3 % response rate. Overall, there were 709 total deaths reported (6.0 %). The mean age at death was 36.4 ± 30.1 years: 330 (46.6 %) were female. Most deaths occurred at home (58.1 % vs. 34.1 % in hospitals). Of the 709 deaths, 237 (33.4 %) were associated with conditions included in our predefined surgical disease category. Abdominal distension/pain was the most commonly associated surgical condition (13.9 %) followed by perinatal bleeding/illness (6.0 %). Among the 237 with surgical conditions, 51 (21.9 %) did not seek medical care, most commonly because of a lack of money (35.3 %) or inability to provide timely care (37.3 %). A large proportion of deaths in Sierra Leone was associated with surgical conditions, the majority of which did not undergo surgical intervention. Our results indicate that to remove barriers to effective surgical care in Sierra Leone policymakers should first focus on relieving financial burdens and increasing access to timely surgical care.

Potential of Brillouin scattering in polymer optical fiber for strain-insensitive high-accuracy temperature sensing.

PubMed

Mizuno, Yosuke; Nakamura, Kentaro

2010-12-01

We investigated the dependences of Brillouin frequency shift (BFS) on strain and temperature in a perfluorinated graded-index polymer optical fiber (PFGI-POF) at 1.55 μm wavelength. They showed negative dependences with coefficients of -121.8 MHz/% and -4.09 MHz/K, respectively, which are -0.2 and -3.5 times as large as those in silica fibers. These unique BFS dependences indicate that the Brillouin scattering in PFGI-POFs has a big potential for strain-insensitive high-accuracy temperature sensing.

Flow velocity measurements with stimulated Rayleigh-Brillouin-gain spectroscopy

NASA Technical Reports Server (NTRS)

Herring, G. C.; Moosmueller, H.; Lee, S. A.; She, C. Y.

1983-01-01

Using stimulated Rayleigh-Brillouin-gain spectroscopy, velocity measurements in an atmospheric-pressure subsonic nitrogen flow with 10 percent uncertainty have been conducted. It is shown that the accuracy of the velocity measurements increases with gas pressure, making this spectroscopic technique ideal for measuring velocity and other parameters of high-pressure (greater than 1-atm) atomic or molecular flows.

Analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, Arun, E-mail: arunshuklaujn@gmail.com; Jat, K. L.

2015-07-31

An analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma has been reported. In the present analytical investigation, the lattice displacement, acousto-optical polarization, susceptibility, acousto-optical gain constant arising due to the induced nonlinear current density and acousto-optical process are deduced in an acoustically perturbed Brillouin active magnetized semiconductor plasma using the hydrodynamical model of plasma and coupled mode scheme. The influence of wave number and magnetic field has been explored. The analysis has been applied to centrosymmetric crystal. Numerical estimates are made for n-type InSb crystal duly irradiated by a frequency doubled 10.6 µm CO{sub 2} laser. It is foundmore » that lattice displacement, susceptibility and acousto-optical gain increase linearly with incident wave number and applied dc magnetic field, while decrease with scattering angle. The gain also increases with electric amplitude of incident laser beam. Results are found to be well in agreement with available literature.« less

Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber

PubMed Central

Zaghloul, Mohamed A. S.; Wang, Mohan; Milione, Giovanni; Li, Ming-Jun; Li, Shenping; Huang, Yue-Kai; Wang, Ting; Chen, Kevin P.

2018-01-01

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μϵ/MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%). PMID:29649148

Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber.

PubMed

Zaghloul, Mohamed A S; Wang, Mohan; Milione, Giovanni; Li, Ming-Jun; Li, Shenping; Huang, Yue-Kai; Wang, Ting; Chen, Kevin P

2018-04-12

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores' temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%).

In vivo measurement of age-related stiffening in the crystalline lens by Brillouin optical microscopy.

PubMed

Scarcelli, Giuliano; Kim, Pilhan; Yun, Seok Hyun

2011-09-21

The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (~1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

A numerical analysis of GeO2-doped multi-step index single-mode fiber for stimulated Brillouin scattering

NASA Astrophysics Data System (ADS)

Xiao, H.; Ren, G.; Dong, Y.; Li, H.; Xiao, S.; Wu, B.; Jian, S.

2018-06-01

A numerical analysis of a GeO2-doped single-mode optical fiber with a multi-step index core toward stimulated Brillouin scattering (SBS) based dual-parameter sensing applications is proposed. Adjusting the parameters in the fiber design, higher-order acoustic modes are sufficiently enhanced, making the fiber feasible for discriminative measurements of temperature and strain in the meantime. Numerical simulations indicate that the Brillouin frequency shifts and peak SBS efficiencies are strongly dependent on the doping concentration and the thickness of low-index ring in the proposed fiber. With appropriate structural and optical parameters, this fiber could support two distinct acoustic modes with comparable peak SBS efficiencies and well-spaced Brillouin frequency shifts. The sensing characteristics contributed by the dual-peak feature in the Brillouin gain spectrum are explored. Calculated accuracies of temperature and strain in simultaneous measurements can be up to 0.64 °C and 15.4 με, respectively. The proposed fiber might have potential applications for long-haul distributed dual-parameter simultaneous measurements.

Imaging of Keratoconic and normal human cornea with a Brillouin imaging system (Conference Presentation)

NASA Astrophysics Data System (ADS)

Besner, Sebastien; Shao, Peng; Scarcelli, Giuliano; Pineda, Roberto; Yun, Seok-Hyun (Andy)

2016-03-01

Keratoconus is a degenerative disorder of the eye characterized by human cornea thinning and morphological change to a more conical shape. Current diagnosis of this disease relies on topographic imaging of the cornea. Early and differential diagnosis is difficult. In keratoconus, mechanical properties are found to be compromised. A clinically available invasive technique capable of measuring the mechanical properties of the cornea is of significant importance for understanding the mechanism of keratoconus development and improve detection and intervention in keratoconus. The capability of Brillouin imaging to detect local longitudinal modulus in human cornea has been demonstrated previously. We report our non-contact, non-invasive, clinically viable Brillouin imaging system engineered to evaluate mechanical properties human cornea in vivo. The system takes advantage of a highly dispersive 2-stage virtually imaged phased array (VIPA) to detect weak Brillouin scattering signal from biological samples. With a 1.5-mW light beam from a 780-nm single-wavelength laser source, the system is able to detect Brillouin frequency shift of a single point in human cornea less than 0.3 second, at a 5μm/30μm lateral/axial resolution. Sensitivity of the system was quantified to be ~ 10 MHz. A-scans at different sample locations on a human cornea with a motorized human interface. We imaged both normal and keratoconic human corneas with this system. Whereas no significantly difference were observed outside keratocnic cones compared with normal cornea, a highly statistically significantly decrease was found in the cone regions.

Transmission dynamics of Ebola virus disease and intervention effectiveness in Sierra Leone

PubMed Central

Fang, Li-Qun; Yang, Yang; Jiang, Jia-Fu; Yao, Hong-Wu; Kargbo, David; Li, Xin-Lou; Jiang, Bao-Gui; Kargbo, Brima; Tong, Yi-Gang; Wang, Ya-Wei; Liu, Kun; Kamara, Abdul; Dafae, Foday; Kanu, Alex; Jiang, Rui-Ruo; Sun, Ye; Sun, Ruo-Xi; Chen, Wan-Jun; Ma, Mai-Juan; Dean, Natalie E.; Thomas, Harold; Longini, Ira M.; Halloran, M. Elizabeth; Cao, Wu-Chun

2016-01-01

Sierra Leone is the most severely affected country by an unprecedented outbreak of Ebola virus disease (EVD) in West Africa. Although successfully contained, the transmission dynamics of EVD and the impact of interventions in the country remain unclear. We established a database of confirmed and suspected EVD cases from May 2014 to September 2015 in Sierra Leone and mapped the spatiotemporal distribution of cases at the chiefdom level. A Poisson transmission model revealed that the transmissibility at the chiefdom level, estimated as the average number of secondary infections caused by a patient per week, was reduced by 43% [95% confidence interval (CI): 30%, 52%] after October 2014, when the strategic plan of the United Nations Mission for Emergency Ebola Response was initiated, and by 65% (95% CI: 57%, 71%) after the end of December 2014, when 100% case isolation and safe burials were essentially achieved, both compared with before October 2014. Population density, proximity to Ebola treatment centers, cropland coverage, and atmospheric temperature were associated with EVD transmission. The household secondary attack rate (SAR) was estimated to be 0.059 (95% CI: 0.050, 0.070) for the overall outbreak. The household SAR was reduced by 82%, from 0.093 to 0.017, after the nationwide campaign to achieve 100% case isolation and safe burials had been conducted. This study provides a complete overview of the transmission dynamics of the 2014−2015 EVD outbreak in Sierra Leone at both chiefdom and household levels. The interventions implemented in Sierra Leone seem effective in containing the epidemic, particularly in interrupting household transmission. PMID:27035948

Quantifying surgical capacity in Sierra Leone: a guide for improving surgical care.

PubMed

Kingham, T Peter; Kamara, Thaim B; Cherian, Meena N; Gosselin, Richard A; Simkins, Meghan; Meissner, Chris; Foray-Rahall, Lynda; Daoh, Kisito S; Kabia, Soccoh A; Kushner, Adam L

2009-02-01

Lack of access to surgical care is a public health crisis in developing countries. There are few data that describe a nation's ability to provide surgical care. This study combines information quantifying the infrastructure, human resources, interventions (ie, procedures), emergency equipment and supplies for resuscitation, and surgical procedures offered at many government hospitals in Sierra Leone. Site visits were performed in 2008 at 10 of the 17 government civilian hospitals in Sierra Leone. The World Health Organization's Tool for Situational Analysis to Assess Emergency and Essential Surgical Care was used to assess surgical capacity. There was a paucity of electricity, running water, oxygen, and fuel at the government hospitals in Sierra Leone. There were only 10 Sierra Leonean surgeons practicing in the surveyed government hospitals. Many procedures performed at most of the hospitals were cesarean sections, hernia repairs, and appendectomies. There were few supplies at any of the hospitals, forcing patients to provide their own. There was a disparity between conditions at the government hospitals and those at the private and mission hospitals. There are severe shortages in all aspects of infrastructure, personnel, and supplies required for delivering surgical care in Sierra Leone. While it will be difficult to improve the infrastructure of government hospitals, training additional personnel to deliver safe surgical care is possible. The situational analysis tool is a valuable mechanism to quantify a nation's surgical capacity. It provides the background data that have been lacking in the discussion of surgery as a public health problem and will assist in gauging the effectiveness of interventions to improve surgical infrastructure and care.

Laryngologist Leon Zamenhof--brother of Dr. Esperanto.

PubMed

Wincewicz, Andrzej; Sulkowska, Mariola; Musiatowicz, Marcin; Sulkowski, Stanislaw

2009-06-01

To reconstruct the biography of the Polish otorhinolaryngologist Leon Zamenhof (1875-1934), a brother of Ludwik Zamenhof, who is famous for invention of the international language Esperanto. Biographical information was collected from pre-World War II resources. Zamenhof developed several important new forms of treatment to help the hearing impaired. Zamenhof was especially interested in the education of deaf children and the therapy necessary to facilitate their integration into society. His significant achievements were a phonetic method of therapy for the hearing impaired and an automatic device for ear insufflation that was considered indispensable in the management of pyorrhea. In addition, Zamenhof initiated various forms of social support among physicians within the medical community of Warsaw, Poland; made health care available to children with hearing impairments; and organized a Jewish school for deaf children. Zamenhof tried to change public attitudes toward deafness, working to promote the integration of the deaf into wider society. He also translated Polish literature into Esperanto. With similar aims to his brother Ludwik, Leon Zamenhof strived to enhance and broaden communication among people who could not hear and to persuade people to change their attitudes about deafness.

Home Alone: Children as Caretakers in Leon, Nicaragua

ERIC Educational Resources Information Center

Dahlblom, Kjerstin; Herrara, Andres Rodriguez; Pena, Rodolfo; Dahlgren, Lars

2009-01-01

This article seeks to explore and understand the life situations of sibling caretakers in poor areas in Leon, Nicaragua. The every day lives for caretakers were studied through observations and interviews with children, informants and parents. The children themselves were satisfied and proud to be trusted as caretakers and felt useful in…

GT-10 - EARTH SKY - COAHUILA & NUEVO LEON, MEXICO

NASA Image and Video Library

1966-07-18

S66-45763 (18-21 July 1966) --- Don Martin Reservoir and Sabinas River Valley area of the States of Coahuila and Nuevo Leon, Mexico, as seen from the Gemini-10 spacecraft. Taken with a J. A. Maurer 70mm camera, using Eastman Kodak, Ektachrome, MS (S.O. 217) color film. Photo credit: NASA

Acoustic properties and density of polyurea at pressure up to 13.5 GPa through Brillouin scattering spectroscopy

NASA Astrophysics Data System (ADS)

Ransom, T. C.; Ahart, Muhtar; Hemley, Russell J.; Roland, C. M.

2018-05-01

Brillouin scattering was performed on an elastomeric polyurea, an important technological polymer. Being widely used for impact modification, of particular interest is its response to extreme pressure conditions. We applied pressures up to 13.5 GPa using a diamond anvil cell and measured the longitudinal and transverse sound velocities via Brillouin light scattering. From these data, the equation of state, the elastic moduli, and Poisson's ratio were obtained. By comparison with previous dilatometry measurements up to 1 GPa, we show how viscoelastic effects can be accounted for in order to obtain an accurate equation of state. Because of the extreme strain-rate hardening of vitrifying polyurea, the property changes associated with its solidification are more subtle in the high frequency Brillouin data than observed in conventional mechanical testing and dilatometry.

Electron Gyro-Harmonic Effects on Ionospheric Stimulated Brillouin Scatter

DTIC Science & Technology

2014-08-21

27709-2211 Brillouin, SBS, emission lines, pump frequency stepping, cyclotron , EIC, airglow, upper hybrid REPORT DOCUMENTATION PAGE 11. SPONSOR...direction and the background magnetic field vector, the excited electrostatic wave could be either ion acoustic (IA) or electrostatic ion cyclotron (EIC...A. Hedberg, B. Lundborg, P. Stubbe, H. Kopka, and M. T. Rietveld (1989), Stimulated electromagnetic emission near electron cyclotron harmonics in

Distributed fiber strain and vibration sensor based on Brillouin optical time-domain reflectometry and polarization optical time-domain reflectometry.

PubMed

Wang, Feng; Zhang, Xuping; Wang, Xiangchuan; Chen, Haisheng

2013-07-15

A distributed fiber strain and vibration sensor which effectively combines Brillouin optical time-domain reflectometry and polarization optical time-domain reflectometry is proposed. Two reference beams with orthogonal polarization states are, respectively, used to perform the measurement. By using the signal obtained from either reference beam, the vibration of fiber can be measured from the polarization effect. After combining the signals obtained by both reference beams, the strain can be measured from the Brillouin effect. In the experiment, 10 m spatial resolution, 0.6 kHz frequency measurement range, 2.5 Hz frequency resolution, and 0.2 MHz uncertainty of Brillouin frequency measurement are realized for a 4 km sensing distance.

The Topp-Leone generalized Rayleigh cure rate model and its application

NASA Astrophysics Data System (ADS)

Nanthaprut, Pimwarat; Bodhisuwan, Winai; Patummasut, Mena

2017-11-01

Cure rate model is one of the survival analysis when model consider a proportion of the censored data. In clinical trials, the data represent time to recurrence of event or death of patients are used to improve the efficiency of treatments. Each dataset can be separated into two groups: censored and uncensored data. In this work, the new mixture cure rate model is introduced based on the Topp-Leone generalized Rayleigh distribution. The Bayesian approach is employed to estimate its parameters. In addition, a breast cancer dataset is analyzed for model illustration purpose. According to the deviance information criterion, the Topp-Leone generalized Rayleigh cure rate model shows better result than the Weibull and exponential cure rate models.

Suppression of stimulated Brillouin scattering in all-solid chalcogenide-tellurite photonic bandgap fiber.

PubMed

Cheng, Tonglei; Liao, Meisong; Gao, Weiqing; Duan, Zhongchao; Suzuki, Takenobu; Ohishi, Yasutake

2012-12-17

A new way to suppress stimulated Brillouin scattering by using an all-solid chalcogenide-tellurite photonic bandgap fiber is presented in the paper. The compositions of the chalcogenide and the tellurite glass are As(2)Se(3) and TeO(2)-ZnO-Li(2)O-Bi(2)O(3). The light and the acoustic wave are confined in the fiber by photonic bandgap and acoustic bandgap mechanism, respectively. When the pump wavelength is within the photonic bandgap and the acoustic wave generated by the pump light is outside the acoustic bandgap, the interaction between the optical and the acoustic modes is very weak, thus stimulated Brillouin scattering is suppressed in the photonic bandgap fiber.

Distributed dynamic large strain optical fiber sensor based on the detection of spontaneous Brillouin scattering.

PubMed

Masoudi, Ali; Belal, Mohammad; Newson, Trevor P

2013-09-01

A Brillouin-based distributed optical fiber dynamic strain sensor is described which converts strain-induced Brillouin frequency shift into optical intensity variations by using an imbalanced Mach-Zhender interferometer. A 3×3 coupler is used at the output of this interferometer to permit differentiate and cross multiply demodulation. The demonstrated sensor is capable of probing dynamic strain disturbances over 2 km of sensing length every 0.5 s up to a strain of 10 mε with an accuracy of ±50 με and spatial resolution of 1.3 m.

Manure nutrient management effects in the Leon River Watershed

USDA-ARS?s Scientific Manuscript database

The Leon River Watershed (LRW) in central Texas is a Benchmark and Special Emphasis watershed within the Conservation Effects Assessment Project (CEAP) located in central Texas. Model simulations from 1977 through 2006 were used to evaluate six manure nutrient management scenarios that reflect reali...

Single-crystal Brillouin spectroscopy with CO{sub 2} laser heating and variable q

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jin S.; Bass, Jay D.; Zhu, Gaohua

2015-06-15

We describe a Brillouin spectroscopy system integrated with CO{sub 2} laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ∼13 GPa, 1300 ± 200 K. The pressure as measured by rubymore » fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (∼141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm)« less

Experimental and numerical study of high order Stokes lines in Brillouin-erbium fiber laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Yijun; College of Physics Science and Engineering Technology, Yichun University, Yichun, Jiangxi Province 336000; Yao, Yong, E-mail: yaoyong@hit.edu.cn

2014-01-28

We experimentally study the dependences of high-order Stokes lines on the erbium-doped fiber (EDF) pump power P{sub EDF}, the Brillouin pump (BP) power P{sub BP}, and its working wavelength in a multiwavelength Brillouin erbium-doped fiber laser (MBEFL). By using the rate and propagation equations, and the coupled wave equations of stimulated Brillouin scattering, we establish a lumped model to describe the MBEFL. Numerical simulations show that the number of Stokes lines can be increased by decreasing the spacing between the BP wavelength and the EDF peak gain or P{sub BP} as long as it is larger than a critical valuemore » P{sub BP}{sup (cr)}=1.7 mW, or by increasing P{sub EDF} without reaching a saturation value P{sub EDF}{sup (cr)}=250 mW. However, when P{sub BP} and P{sub EDF} are varied beyond P{sub BP}{sup (cr)} and P{sub EDF}{sup (cr)}, respectively, the number of Stokes lines is reduced, accompanied by some self-lasing cavity modes. These results by numerical simulation are consistent with experimental observations from the MBEFL.« less

Undiagnosed Acute Viral Febrile Illnesses, Sierra Leone

DTIC Science & Technology

2014-07-01

Sierra Leone in West Africa is in a Lassa fever – hyperendemic region that also includes Guinea and Li- beria. Each year...suspected Lassa fever cases result in submission of ≈500–700 samples to the Kenema Govern- ment Hospital Lassa Diagnostic Laboratory in eastern Si- erra...patients have acute diseases of unknown origin. To investigate what other ar- thropod-borne and hemorrhagic fever viral diseases might cause serious

Assessing the effect of a high-fat diet on rodents' adipose tissue using Brillouin and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Troyanova-Wood, Maria; Gobbell, Cassidy; Meng, Zhaokai; Yakovlev, Vladislav V.

2016-03-01

The purpose of this study is to evaluate the effect of a high-lipid diet on elasticity of adipose tissue. We employed dual Raman/Brillouin microspectroscopy to analyze brown and white adipose tissues obtained from adult rats. The rats were divided into two groups, one of which received a high-fat feed, while the other served as a control. We hypothesized that the changes in the elasticity of adipose tissues between the two groups can be successfully assessed using Brillouin spectroscopy. We found that the brown adipose tissue possessed a lesser Brillouin shift than the white adipose within each group and that the elastic modulus of both adipose tissues increases in the high-fat diet group. The Raman spectra provided supplementary chemical information and indicated an increase in the lipid-to-protein ratio in the brown adipose, but not in the white adipose.

All-optical signal processing using dynamic Brillouin gratings

PubMed Central

Santagiustina, Marco; Chin, Sanghoon; Primerov, Nicolay; Ursini, Leonora; Thévenaz, Luc

2013-01-01

The manipulation of dynamic Brillouin gratings in optical fibers is demonstrated to be an extremely flexible technique to achieve, with a single experimental setup, several all-optical signal processing functions. In particular, all-optical time differentiation, time integration and true time reversal are theoretically predicted, and then numerically and experimentally demonstrated. The technique can be exploited to process both photonic and ultra-wide band microwave signals, so enabling many applications in photonics and in radio science. PMID:23549159

Landsat-Derived Estimates of Mangrove Extents in the Sierra Leone Coastal Landscape Complex during 1990–2016

PubMed Central

Trzaska, Sylwia

2017-01-01

This study provides the first assessment of decadal changes in mangrove extents in Sierra Leone. While significant advances have been made in mangrove mapping using remote sensing, no study has documented long-term changes in mangrove extents in Sierra Leone—one of the most vulnerable countries in West Africa. Such understanding is critical for devising regional management strategies that can support local livelihoods. We utilize multi-date Landsat data and cloud computational techniques to quantify spatiotemporal changes in land cover, with focus on mangrove ecosystems, for 1990–2016 along the coast of Sierra Leone. We specifically focus on four estuaries—Scarcies, Sierra Leone, Yawri Bay, and Sherbro. We relied on the k-means approach for an unsupervised classification, and validated the classified map from 2016 using ground truth data collected from Sentinel-2 and high-resolution images and during field research (accuracy: 95%). Our findings indicate that the Scarcies river estuary witnessed the greatest mangrove loss since 1990 (45%), while the Sierra Leone river estuary experienced mangrove gain over the last 26 years (22%). Overall, the Sierra Leone coast lost 25% of its mangroves between 1990 and 2016, with the lowest coverage in 2000, during the period of civil war (1991–2002). However, natural mangrove dynamics, as supported by field observations, indicate the potential for regeneration and sustainability under carefully constructed management strategies. PMID:29267247

Few-mode fiber based distributed curvature sensor through quasi-single-mode Brillouin frequency shift.

PubMed

Wu, Hao; Wang, Ruoxu; Liu, Deming; Fu, Songnian; Zhao, Can; Wei, Huifeng; Tong, Weijun; Shum, Perry Ping; Tang, Ming

2016-04-01

We proposed and demonstrated a few-mode fiber (FMF) based optical-fiber sensor for distributed curvature measurement through quasi-single-mode Brillouin frequency shift (BFS). By central-alignment splicing FMF and single-mode fiber (SMF) with a fusion taper, a SMF-components-compatible distributed curvature sensor based on FMF is realized using the conventional Brillouin optical time-domain analysis system. The distributed BFS change induced by bending in FMF has been theoretically and experimentally investigated. The precise BFS response to the curvature along the fiber link has been calibrated. A proof-of-concept experiment is implemented to validate its effectiveness in distributed curvature measurement.

Double spacing multi-wavelength Brillouin Raman fiber laser of eight-shaped structure utilizing Raman amplifier

NASA Astrophysics Data System (ADS)

Madin, M. Sya'aer; Ahmad Hambali, N. A. M.; Shahimin, M. M.; Wahid, M. H. A.; Roshidah, N.; Azaidin, M. A. M.

2017-02-01

In this paper, double frequency spacing of multi-wavelength Brillouin Raman fiber laser utilizing eight-shaped structure in conjunction with Raman amplifier is simulated and demonstrated using Optisys software. Double frequency multiwavelength Brillouin Raman fiber laser is one of the solution for single frequency spacing channel de-multiplexing from narrow single spacing in the communication systems. The eight-shaped structure has the ability to produce lower noise and double frequency spacing. The 7 km of single mode fiber acting as a nonlinear medium for the generation of Stimulated Brillouin Scattering and Stimulated Raman Scattering. As a results, the optimum results are recorded at 1450 nm of RP power at 22 dBm and 1550 nm of BP power at 20 dBm. These parameters provide a high output peak power, gain and average OSNR. The highest peak power of Stokes 1 is recorded at 90% of coupling ratio which is 29.88 dBm. It is found that the maximum gain and average OSNR of about 1.23 dB and 63.74 dB.

Exploiting the locality of periodic subsystem density-functional theory: efficient sampling of the Brillouin zone.

PubMed

Genova, Alessandro; Pavanello, Michele

2015-12-16

In order to approximately satisfy the Bloch theorem, simulations of complex materials involving periodic systems are made n(k) times more complex by the need to sample the first Brillouin zone at n(k) points. By combining ideas from Kohn-Sham density-functional theory (DFT) and orbital-free DFT, for which no sampling is needed due to the absence of waves, subsystem DFT offers an interesting middle ground capable of sizable theoretical speedups against Kohn-Sham DFT. By splitting the supersystem into interacting subsystems, and mapping their quantum problem onto separate auxiliary Kohn-Sham systems, subsystem DFT allows an optimal topical sampling of the Brillouin zone. We elucidate this concept with two proof of principle simulations: a water bilayer on Pt[1 1 1]; and a complex system relevant to catalysis-a thiophene molecule physisorbed on a molybdenum sulfide monolayer deposited on top of an α-alumina support. For the latter system, a speedup of 300% is achieved against the subsystem DTF reference by using an optimized Brillouin zone sampling (600% against KS-DFT).

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

PubMed Central

Scarcelli, Giuliano; Kim, Pilhan; Yun, Seok Hyun

2011-01-01

Abtract The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (∼1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology. PMID:21943436

Good laboratory practices guarantee biosafety in the Sierra Leone-China friendship biosafety laboratory.

PubMed

Wang, Qin; Zhou, Wei-Min; Zhang, Yong; Wang, Huan-Yu; Du, Hai-Jun; Nie, Kai; Song, Jing-Dong; Xiao, Kang; Lei, Wen-Wen; Guo, Jian-Qiang; Wei, He-Jiang; Cai, Kun; Wang, Yan-Hai; Wu, Jiang; Kamara, Gerard; Kamara, Idrissa; Wei, Qiang; Liang, Mi-Fang; Wu, Gui-Zhen; Dong, Xiao-Ping

2016-06-23

The outbreak of Ebola virus disease (EVD) in West Africa between 2014 and 2015 was the largest EDV epidemic since the identification of Ebola virus (EBOV) in 1976, and the countries most strongly affected were Sierra Leone, Guinea, and Liberia. The Sierra Leone-China Friendship Biological Safety Laboratory (SLE-CHN Biosafety Lab), a fixed Biosafety Level 3 laboratory in the capital city of Sierra Leone, was established by the Chinese government and has been active in EBOV detection since 11 March 2015. Complete management and program documents were created for the SLE-CHN Biosafety Lab, and it was divided into four zones (the green, yellow, brown, and red zones) based on the risk assessment. Different types of safe and appropriate personnel protection equipment (PPE) are used in different zones of the laboratory, and it fully meets the Biosafety Level 3 laboratory standards of the World Health Organization. Good preparedness, comprehensive risk assessment and operation documents, appropriate PPE, effective monitoring and intensive training, together with well-designed and reasonable laboratory sectioning are essential for guaranteeing biosafety.

Sequence Variability and Geographic Distribution of Lassa Virus, Sierra Leone

PubMed Central

Stockelman, Michael G.; Moses, Lina M.; Park, Matthew; Stenger, David A.; Ansumana, Rashid; Bausch, Daniel G.; Lin, Baochuan

2015-01-01

Lassa virus (LASV) is endemic to parts of West Africa and causes highly fatal hemorrhagic fever. The multimammate rat (Mastomys natalensis) is the only known reservoir of LASV. Most human infections result from zoonotic transmission. The very diverse LASV genome has 4 major lineages associated with different geographic locations. We used reverse transcription PCR and resequencing microarrays to detect LASV in 41 of 214 samples from rodents captured at 8 locations in Sierra Leone. Phylogenetic analysis of partial sequences of nucleoprotein (NP), glycoprotein precursor (GPC), and polymerase (L) genes showed 5 separate clades within lineage IV of LASV in this country. The sequence diversity was higher than previously observed; mean diversity was 7.01% for nucleoprotein gene at the nucleotide level. These results may have major implications for designing diagnostic tests and therapeutic agents for LASV infections in Sierra Leone. PMID:25811712

Intra-Brillouin-zone bandgaps due to periodic misalignment in one-dimensional magnetophotonic crystals

NASA Astrophysics Data System (ADS)

Wang, Fei; Lakhtakia, Akhlesh

2008-01-01

One-dimensional (1D) magnetophotonic crystals (MPCs) can incorporate optical gyrotropy induced by a bias magnetic field, crystalline misalignment, and differential linear birefringence in a single photonic-crystal structure. A 1D MPC whose unit cell contains two layers—one magnetophotonic, the other not—displays intra-Brillouin-zone photonic bandgaps (PBGs) in the Brillouin diagram. While the optical gyrotropy makes the PBG bandwidths tunable by a bias magnetic field, the bicrystalline misalignment modifies and can even trump this magnetic tunability. Magnetic tunability is greatly affected by a proper selection of the two materials; e.g., a large birefringence ratio between the two layers can dramatically enhance the magnetic tunability of the MPC. We also expect our 1D MPCs to be useful for detecting magnetic fields.

Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Raghunathan, Raksha; Zhang, Jitao; Wu, Chen; Rippy, Justin; Singh, Manmohan; Larin, Kirill V.; Scarcelli, Giuliano

2017-08-01

Embryogenesis is regulated by numerous changes in mechanical properties of the cellular microenvironment. Thus, studying embryonic mechanophysiology can provide a more thorough perspective of embryonic development, potentially improving early detection of congenital abnormalities as well as evaluating and developing therapeutic interventions. A number of methods and techniques have been used to study cellular biomechanical properties during embryogenesis. While some of these techniques are invasive or involve the use of external agents, others are compromised in terms of spatial and temporal resolutions. We propose the use of Brillouin microscopy in combination with optical coherence tomography (OCT) to measure stiffness as well as structural changes in a developing embryo. While Brillouin microscopy assesses the changes in stiffness among different organs of the embryo, OCT provides the necessary structural guidance.

[94 km Brillouin distributed optical fiber sensors based on ultra-long fiber ring laser pumping].

PubMed

Yuan, Cheng-Xu; Wang, Zi-Nan; Jia, Xin-Hong; Li, Jin; Yan, Xiao-Dong; Cui, An-Bin

2014-05-01

A novel optical amplification configuration based on ultra-long fiber laser with a ring cavity was proposed and applied to Brillouin optical time-domain analysis (BOTDA) sensing system, in order to extend the measurement distance significantly. The parameters used in the experiment were optimized, considering the main limitations of the setup, such as depletion, self-phase modulation (SPM) and pump-signal relative intensity noise (RIN) transfer. Through analyzing Brillouin gain spectrum, we demonstrated distributed sensing over 94 km of standard single-mode fiber with 3 meter spatial resolution and strain/temperature accuracy of 28 /1. 4 degree C.

Macroeconomic costs of the unmet burden of surgical disease in Sierra Leone: a retrospective economic analysis

PubMed Central

Kamara, Thaim B; Lavy, Christopher B D; Leather, Andy J M; Bolkan, Håkon A

2018-01-01

Objectives The Lancet Commission on Global Surgery estimated that low/middle-income countries will lose an estimated cumulative loss of US$12.3 trillion from gross domestic product (GDP) due to the unmet burden of surgical disease. However, no country-specific data currently exist. We aimed to estimate the costs to the Sierra Leone economy from death and disability which may have been averted by surgical care. Design We used estimates of total, met and unmet need from two main sources—a cluster randomised, cross-sectional, countrywide survey and a retrospective, nationwide study on surgery in Sierra Leone. We calculated estimated disability-adjusted life years from morbidity and mortality for the estimated unmet burden and modelled the likely economic impact using three different methods—gross national income per capita, lifetime earnings foregone and value of a statistical life. Results In 2012, estimated, discounted lifetime losses to the Sierra Leone economy from the unmet burden of surgical disease was between US$1.1 and US$3.8 billion, depending on the economic method used. These lifetime losses equate to between 23% and 100% of the annual GDP for Sierra Leone. 80% of economic losses were due to mortality. The incremental losses averted by scale up of surgical provision to the Lancet Commission target of 80% were calculated to be between US$360 million and US$2.9 billion. Conclusion There is a large economic loss from the unmet need for surgical care in Sierra Leone. There is an immediate need for massive investment to counteract ongoing economic losses. PMID:29540407

Remote-sensing gas measurements with coherent Rayleigh-Brillouin scattering

DOE PAGES

Gerakis, A.; Shneider, M. N.; Stratton, B. C.

2016-07-21

Here, we measure the coherent Rayleigh-Brillouin scattering (CRBS) signal integral as a function of the recorded gas pressure in He, Co 2, SF 6, and air, and confirm the already established quadratic dependence of the signal on the gas density. Finally, we propose the use of CRBS as an effective diagnostic for the remote measurement of gas' density (pressure) and temperature, as well as polarizability, for gases of known composition.

One-laser-based generation/detection of Brillouin dynamic grating and its application to distributed discrimination of strain and temperature.

PubMed

Zou, Weiwen; He, Zuyuan; Hotate, Kazuo

2011-01-31

This paper presents a novel scheme to generate and detect Brillouin dynamic grating in a polarization-maintaining optical fiber based on one laser source. Precise measurement of Brillouin dynamic grating spectrum is achieved benefiting from that the pump, probe and readout waves are coherently originated from the same laser source. Distributed discrimination of strain and temperature is also achieved with high accuracy.

Signatures of chaos in the Brillouin zone.

PubMed

Barr, Aaron; Barr, Ariel; Porter, Max D; Reichl, Linda E

2017-10-01

When the classical dynamics of a particle in a finite two-dimensional billiard undergoes a transition to chaos, the quantum dynamics of the particle also shows manifestations of chaos in the form of scarring of wave functions and changes in energy level spacing distributions. If we "tile" an infinite plane with such billiards, we find that the Bloch states on the lattice undergo avoided crossings, energy level spacing statistics change from Poisson-like to Wigner-like, and energy sheets of the Brillouin zone begin to "mix" as the classical dynamics of the billiard changes from regular to chaotic behavior.

Interaction physics for the stimulated Brillouin scattering of a laser in laser driven fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Pinki; Gupta, D.N.; Avinash, K., E-mail: dngupta@physics.du.ac.in

2014-07-01

Energy exchange between pump wave and ion-acoustic wave during the stimulated Brillouin Scattering process in relativistic laser-plasma interactions is studied, including the effect of damping coefficient of electron-ion collision by obeying the energy and momentum conservations. The variations of plasma density and damping coefficient of electron-ion collision change the amplitudes of the interacting wave. The relativistic mass effect modifies the dispersion relations of the interacting waves and consequently, the energy exchange during the stimulated Brillouin Scattering is affected. The collisional damping of electron-ion collision in the plasma is shown to have an important effect on the evolution of the interactingmore » waves. (author)« less

Power in Practice: Trade Union Education in Sierra Leone

ERIC Educational Resources Information Center

Stirling, John

2013-01-01

This article presents an analysis of the development of a trade union education program in Sierra Leone in the geo-historical context of British colonialism. It places the argument in relation to the contradictory trends of trade unionism more generally and alongside their antagonistic cooperation with capitalism. It discusses the limits and…

Strain measurement using a Brillouin optical time domain reflectometer for development of aircraft structure health monitoring system

NASA Astrophysics Data System (ADS)

Shimizu, Takayuki; Yari, Takashi; Nagai, Kanehiro; Takeda, Nobuo

2001-07-01

We conducted theoretical and experimental approaches for applying Brillouin optical time domain reflectometer (BOTDR) to aircraft and spacecraft structure health monitoring system. Firstly, distributed strain was measured by BOTDR under 3-point bending test and a spatial resolution was enhanced up to 0.5m using Brillouin spectrum analysis and processing though the device used in this experiment had a spatial resolution of 2m normally. Secondly, dynamic strain measurement was executed under cyclic loading conditions. Brillouin spectrum measured under dynamic conditions is equivalent to superposed spectrum using many spectra measured under static loading conditions. As the measured spectrum was decomposed into many spectra in static loading state, the strain amplitude and its ratio could be estimated. Thirdly, strain and temperature could be measured independently using combined system of BOTDR and fiber Bragg grating (FBG) with wavelength division multiplexing (WDM). Additionally, the application of BOTDR sensing system was shown for a prototype carbon fiber reinforced plastic (CFRP) liquid hydrogen (LH2) tank under cryogenic condition.

Stimulated Brillouin Scattering Phase Conjugation in Fiber Optic Waveguides

DTIC Science & Technology

2008-07-01

61] The discrepancy is reduced since the effective length of the interaction may be limited by the coherence length of the signal laser as in Eq...these cases, the coherence length of the pulsed laser typically limits the effective length of the Brillouin scattering interaction. Long... coherence length lasers with long fiber SBS media have been used to reduce threshold energy, but as indicated at the end of Chapter 2, this has produced

Military Interventions in Sierra Leone: Lessons from a Failed State

DTIC Science & Technology

2008-01-01

enslaved from Sierra Leone were shipped to the Caribbean and Brazil . This heinous trade lasted for over 100 years. Competing religious...Bana. Map 6. Operation BARRAS area of operations. 67 Magbeni and Gberi Bana were surrounded by dense jungle vegeta­ tion, mangrove swamps, murky

Leon Cooper's Perspective on Teaching Science: An Interview Study

ERIC Educational Resources Information Center

Niaz, Mansoor; Klassen, Stephen; McMillan, Barbara; Metz, Don

2010-01-01

The authors of this paper portray the perspective of Professor Leon Cooper, a theoretical physicist, Nobel laureate, active researcher, and physics textbook author, on teaching science and on the nature of science (NOS). The views presented emerged from an interview prepared by the authors and responded to in writing by Professor Cooper. Based on…

Analysis of water-surface profiles in Leon County and the city of Tallahassee, Florida

USGS Publications Warehouse

Franklin, M.A.; Orr, R.A.

1987-01-01

Water surface profiles for the 10-, 25-, 50-, and 100-yr recurrence interval floods for most of the streams that drain developing areas of Leon County and the city of Tallahassee are presented. The principal streams studied are in the Lake Munson, Lake Lafayette, and Lake Jackson basins Peak discharges were computed from regression equations based on information gained from 15 streamflow stations in the area. Standard step-backwater procedures were used to determine the water-surface elevations for the streams. The flood elevations were generally higher than those in the Flood Insurance Studies for Tallahassee (1976) and Leon County (1982). The primary reason for the higher profiles is that peak discharges used in this report are larger than those used previously, largely due to changes in land use. The flood profiles for Bradford Brook, North Branch Gum Creek, and West Branch Gum Creek generally match those in the Leon County Flood Insurance Studies. Channel improvements in some areas would lower the flood elevation in that area, but would probably increase flooding downstream. (Lantz-PTT)

Population education in Sierra Leone.

PubMed

Lucan, T A

1985-06-01

The 1977 Sierra Leone 3 year population education project had 5 objectives: 1) to develop a core of Sierra Leoneans qualified in population education, 2) to integrate population education concepts into the curriculum for secondary schools and teachers colleges, 3) to train teachers already engaged in trial teaching in pilot schools in the new integrated curricula to give support to their colleagues, 4) to integrate population education into the whole Sierra Leone educational system, and 5) to create an awareness of the implications of population growth on the socioeconomic development of the country. A 1977 seminar on the Social Studies and Population Education Program discussed population issues and economic and social development. The strategy recommended at the seminar was that both the minor and the major revision approaches be used in the integration of population education concepts into the existing curriculum of the National Program in Social Studies for the lower secondary level. A Spiral Curriculum was established in 1981 constructed of 6 topics: 1) man's origins, development, and characteristics; 2) man's environment; 3) man's culture; 4) population and resources; 5) communication in the service of man; and 6) global issues-achievement and problems. Both at in-service and at pre-servicetraining, the enquiry method of teaching was emphasized. By the end of December 1981, the curriculum in Social Studies integrated with Population Education was completed for secondary schools and secondary teachers' colleges. The availability of the textbooks that secondary school students will take to their homes for their parents to read will contribute immensely to the attainment of the development objective of creating an awareness of the implications and consequences of population growth on the socioeconomic development of the country.

Optical Sensors Using Stimulated Brillouin Scattering

NASA Technical Reports Server (NTRS)

Christensen, Caleb A (Inventor); Zavriyev, Anton (Inventor)

2017-01-01

A method for enhancing a sensitivity of an optical sensor having an optical cavity counter-propagates beams of pump light within the optical cavity to produce scattered light based on Stimulated Brillouin Scattering (SBS). The properties of the pump light are selected to generate fast-light conditions for the scattered light, such that the scattered light includes counter-propagating beams of fast light. The method prevents the pump light from resonating within the optical cavity, while allowing the scattered light to resonate within the optical cavity. At least portions of the scattered light are interfered outside of the optical cavity to produce a beat note for a measurement of the optical sensor. The disclosed method is particularly applicable to optical gyroscopes.

The role of cell body density in ruminant retina mechanics assessed by atomic force and Brillouin microscopy

NASA Astrophysics Data System (ADS)

Weber, Isabell P.; Yun, Seok Hyun; Scarcelli, Giuliano; Franze, Kristian

2017-12-01

Cells in the central nervous system (CNS) respond to the stiffness of their environment. CNS tissue is mechanically highly heterogeneous, thus providing motile cells with region-specific mechanical signals. While CNS mechanics has been measured with a variety of techniques, reported values of tissue stiffness vary greatly, and the morphological structures underlying spatial changes in tissue stiffness remain poorly understood. We here exploited two complementary techniques, contact-based atomic force microscopy and contact-free Brillouin microscopy, to determine the mechanical properties of ruminant retinae, which are built up by different tissue layers. As in all vertebrate retinae, layers of high cell body densities (‘nuclear layers’) alternate with layers of low cell body densities (‘plexiform layers’). Different tissue layers varied significantly in their mechanical properties, with the photoreceptor layer being the stiffest region of the retina, and the inner plexiform layer belonging to the softest regions. As both techniques yielded similar results, our measurements allowed us to calibrate the Brillouin microscopy measurements and convert the Brillouin shift into a quantitative assessment of elastic tissue stiffness with optical resolution. Similar as in the mouse spinal cord and the developing Xenopus brain, we found a strong correlation between nuclear densities and tissue stiffness. Hence, the cellular composition of retinae appears to strongly contribute to local tissue stiffness, and Brillouin microscopy shows a great potential for the application in vivo to measure the mechanical properties of transparent tissues.

Temperature-compensated distributed hydrostatic pressure sensor with a thin-diameter polarization-maintaining photonic crystal fiber based on Brillouin dynamic gratings.

PubMed

Teng, Lei; Zhang, Hongying; Dong, Yongkang; Zhou, Dengwang; Jiang, Taofei; Gao, Wei; Lu, Zhiwei; Chen, Liang; Bao, Xiaoyi

2016-09-15

A temperature-compensated distributed hydrostatic pressure sensor based on Brillouin dynamic gratings (BDGs) is proposed and demonstrated experimentally for the first time, to the best of our knowledge. The principle is to measure the hydrostatic pressure induced birefringence changes through exciting and probing the BDGs in a thin-diameter pure silica polarization-maintaining photonic crystal fiber. The temperature cross-talk to the hydrostatic pressure sensing can be compensated through measuring the temperature-induced Brillouin frequency shift (BFS) changes using Brillouin optical time-domain analysis. A distributed measurement of hydrostatic pressure is demonstrated experimentally using a 4-m sensing fiber, which has a high sensitivity, with a maximum measurement error less than 0.03 MPa at a 20-cm spatial resolution.

Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

NASA Astrophysics Data System (ADS)

Balinskiy, Michael; Kargar, Fariborz; Chiang, Howard; Balandin, Alexander A.; Khitun, Alexander G.

2018-05-01

This article reports results of experimental investigation of the spin wave interference over large distances in the Y3Fe2(FeO4)3 waveguide using Brillouin-Mandelstam spectroscopy. Two coherent spin waves are excited by the micro-antennas fabricated at the edges of the waveguide. The amplitudes of the input spin waves are adjusted to provide approximately the same intensity in the central region of the waveguide. The relative phase between the excited spin waves is controlled by the phase shifter. The change of the local intensity distribution in the standing spin wave is monitored using Brillouin-Mandelstam light scattering spectroscopy. Experimental data demonstrate the oscillation of the scattered light intensity depending on the relative phase of the interfering spin waves. The oscillations of the intensity, tunable via the relative phase shift, are observed as far as 7.5 mm away from the spin-wave generating antennas at room temperature. The obtained results are important for developing techniques for remote control of spin currents, with potential applications in spin-based memory and logic devices.

First record of Tenuipalpus uvae De Leon, 1962 (Acari: Tenuipalpidae) in Brazil

USDA-ARS?s Scientific Manuscript database

This is the first record of Tenuipalpus uvae De Leon (Tenuipalpidae) in Brazil. Specimens were collected from Spondias mombin L. (Anacardiaceae) in the states of Amapa (Northern Brazil) and Pernambuco (northeast)....

Brillouin Scattering of Picosecond Laser Pulses in Preformed, Short-Scale-Length Plasmas

NASA Astrophysics Data System (ADS)

Gaeris, A. C.; Fisher, Y.; Delettrez, J. A.; Meyerhofer, D. D.

1996-11-01

Brillouin scattering (BS) has been studied in short-scale-length, preformed plasmas. The backscattered and specularly reflected light resulting from the interaction of high-power picosecond pulses with preformed silicon plasmas has been measured. A first laser pulse forms a short-scale-length plasma -- without significant BS -- while a second delayed pulse interacts with an expanded, drifting underdense region of the plasma with density scale length (0 <= Ln <= 600 λ _L). The pulses are generated at λ L = 1054 nm, with intensities up to 10^16 W/cm^2. The backscattered light spectra, threshold intensities, and enhanced reflectivities have been determined for different plasma-density scale lengths and are compared to Liu, Rosenbluth, and White's(C. S. Liu, M. N. Rosenbluth, and R. B. White, Phys. Fluids 17, 1211 (1974).) WKB treatment of stimulated Brillouin scattering in inhomogeneous drifting plasmas. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

Suppression of stimulated Brillouin instability of a beat-wave of two lasers in multiple-ion-species plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Pinki; Gupta, D. N., E-mail: dngupta@physics.du.ac.in; Avinash, K.

2016-01-15

Stimulated Brillouin instability of a beat-wave of two lasers in plasmas with multiple-ion-species (negative-ions) was studied. The inclusion of negative-ions affects the growth of ion-acoustic wave in Brillouin scattering. Thus, the growth rate of instability is suppressed significantly by the density of negative-ions. To obey the phase-matching condition, the growth rate of the instability attains a maxima for an appropriate scattering angle (angle between the pump and scattered sideband waves). This study would be technologically important to have diagnostics in low-temperature plasmas.

Macroeconomic costs of the unmet burden of surgical disease in Sierra Leone: a retrospective economic analysis.

PubMed

Grimes, Caris E; Quaife, Matthew; Kamara, Thaim B; Lavy, Christopher B D; Leather, Andy J M; Bolkan, Håkon A

2018-03-14

The Lancet Commission on Global Surgery estimated that low/middle-income countries will lose an estimated cumulative loss of US$12.3 trillion from gross domestic product (GDP) due to the unmet burden of surgical disease. However, no country-specific data currently exist. We aimed to estimate the costs to the Sierra Leone economy from death and disability which may have been averted by surgical care. We used estimates of total, met and unmet need from two main sources-a cluster randomised, cross-sectional, countrywide survey and a retrospective, nationwide study on surgery in Sierra Leone. We calculated estimated disability-adjusted life years from morbidity and mortality for the estimated unmet burden and modelled the likely economic impact using three different methods-gross national income per capita, lifetime earnings foregone and value of a statistical life. In 2012, estimated, discounted lifetime losses to the Sierra Leone economy from the unmet burden of surgical disease was between US$1.1 and US$3.8 billion, depending on the economic method used. These lifetime losses equate to between 23% and 100% of the annual GDP for Sierra Leone. 80% of economic losses were due to mortality. The incremental losses averted by scale up of surgical provision to the Lancet Commission target of 80% were calculated to be between US$360 million and US$2.9 billion. There is a large economic loss from the unmet need for surgical care in Sierra Leone. There is an immediate need for massive investment to counteract ongoing economic losses. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Geoheritage value of the UNESCO site at Leon Viejo and Momotombo volcano, Nicaragua

NASA Astrophysics Data System (ADS)

van Wyk de Vries, Benjamin; Navarro, Martha; Espinoza, Eveling; Delgado, Hugo

2017-04-01

The Momotombo volcano has a special place in the history of Nicaragua. It is perfectly visible from the Capital, Managua, and from the major city of Leon. The old capital "Leon Viejo", founded in 1524 was abandoned in 1610, after a series of earthquakes and some major eruptions from Momotombo. The site was subsequently covered by Momotombo ash. A major geothermal power plant stands at the base of the volcano. Momotombo had been dormant for a hundred years, but had maintained high fumarole temperatures (900°C), indicating magma had been close to the surface for decades. In recent years, seismic activity has increased around the volcano. In December 2015, after a short ash eruption phase the volcano erupted lava, then a string of Vulcanian explosions. The volcano is now in a phase of small Vulcanian explosions and degassing. The Leon Viejo World Heritage site is at risk to mainly ash fall from the volcano, but the abandonment of the old city was primarily due to earthquakes. Additional risks come from high rainfall during hurricanes. There is an obvious link between the cultural site (inscribed under UNESCO cultural criteria) and the geological environment. First, the reactivation of Momotombo volcano makes it more important to revise the hazard of the site. At the same time, Leon Viejo can provide a portal for outreach related to the volcano and for geological risk in general. To maximise this, we provide a geosite inventory of the main features of Momotombo, and it's environs, that can be used as the first base for such studies. The volcano was visited by many adventure tourists before the 2015/2016 eruption, but is out of bounds at present. Alternative routes, around the volcano could be made, to adapt to the new situation and to show to visitors more of the geodiversity of this fascinating volcano-tectonic and cultural area.

Relativistic Eulerian Vlasov simulations of the amplification of seed pulses by Brillouin backscattering in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoucri, M., E-mail: Shoucri.Magdi@ireq.ca; Matte, J.-P.; Vidal, F.

We apply an Eulerian Vlasov code to study the amplification by Brillouin scattering of a short seed laser pulse by a long pump laser pulse in an underdense plasma. The stimulated Brillouin backscattering interaction is the coupling of the pump and seed electromagnetic waves propagating in opposite directions, and the ion plasma wave. The code solves the one-dimensional relativistic Vlasov-Maxwell set of equations. Large amplitude ion waves are generated. In the simulations we present, the density plateau of the plasma is n{sub e}=0.3 n{sub c} (n{sub c} is the critical density), which excludes spurious stimulated Raman scattering amplification (which can occurmore » only if n{sub e}« less

Phylogenetic analysis of West Nile virus, Nuevo Leon State, Mexico.

PubMed

Blitvich, Bradley J; Fernández-Salas, Ildefonso; Contreras-Cordero, Juan F; Loroño-Pino, María A; Marlenee, Nicole L; Díaz, Francisco J; González-Rojas, José I; Obregón-Martínez, Nelson; Chiu-García, Jorge A; Black, William C; Beaty, Barry J

2004-07-01

West Nile virus RNA was detected in brain tissue from a horse that died in June 2003 in Nuevo Leon State, Mexico. Nucleotide sequencing and phylogenetic analysis of the premembrane and envelope genes showed that the virus was most closely related to West Nile virus isolates collected in Texas in 2002.

Viscoelasticity of amyloid plaques in transgenic mouse brain studied by Brillouin microspectroscopy and correlative Raman analysis.

PubMed

Mattana, Sara; Caponi, Silvia; Tamagnini, Francesco; Fioretto, Daniele; Palombo, Francesca

2017-11-01

Amyloidopathy is one of the most prominent hallmarks of Alzheimer's disease (AD), the leading cause of dementia worldwide, and is characterized by the accumulation of amyloid plaques in the brain parenchyma. The plaques consist of abnormal deposits mainly composed of an aggregation-prone protein fragment, β -amyloid 1-40/1-42, into the extracellular matrix. Brillouin microspectroscopy is an all-optical contactless technique that is based on the interaction between visible light and longitudinal acoustic waves or phonons , giving access to the viscoelasticity of a sample on a subcellular scale. Here, we describe the first application of micromechanical mapping based on Brillouin scattering spectroscopy to probe the stiffness of individual amyloid plaques in the hippocampal part of the brain of a β -amyloid overexpressing transgenic mouse. Correlative analysis based on Brillouin and Raman microspectroscopy showed that amyloid plaques have a complex structure with a rigid core of β -pleated sheet conformation ( β -amyloid) protein surrounded by a softer ring-shaped region richer in lipids and other protein conformations. These preliminary results give a new insight into the plaque biophysics and biomechanics, and a valuable contrast mechanism for the study and diagnosis of amyloidopathy.

Viscoelasticity of amyloid plaques in transgenic mouse brain studied by Brillouin microspectroscopy and correlative Raman analysis

PubMed Central

Mattana, Sara; Caponi, Silvia; Tamagnini, Francesco; Fioretto, Daniele; Palombo, Francesca

2017-01-01

Amyloidopathy is one of the most prominent hallmarks of Alzheimer’s disease (AD), the leading cause of dementia worldwide, and is characterized by the accumulation of amyloid plaques in the brain parenchyma. The plaques consist of abnormal deposits mainly composed of an aggregation-prone protein fragment, β-amyloid 1-40/1-42, into the extracellular matrix. Brillouin microspectroscopy is an all-optical contactless technique that is based on the interaction between visible light and longitudinal acoustic waves or phonons, giving access to the viscoelasticity of a sample on a subcellular scale. Here, we describe the first application of micromechanical mapping based on Brillouin scattering spectroscopy to probe the stiffness of individual amyloid plaques in the hippocampal part of the brain of a β-amyloid overexpressing transgenic mouse. Correlative analysis based on Brillouin and Raman microspectroscopy showed that amyloid plaques have a complex structure with a rigid core of β-pleated sheet conformation (β-amyloid) protein surrounded by a softer ring-shaped region richer in lipids and other protein conformations. These preliminary results give a new insight into the plaque biophysics and biomechanics, and a valuable contrast mechanism for the study and diagnosis of amyloidopathy. PMID:29151920

[Adverse reactions to mosquito bites in scholars from Monterrey, Nuevo Leon, Mexico].

PubMed

Manrique López, María Amelia; González Díaz, Sandra N; Arias Cruz, Alfredo; Sedó Mejía, Giovanni A; Canseco Villarreal, José Ignacio; Gómez Retamoza, Ernesto Antonio; Padrón López, Olga Magdalena; Cruz Moreno, Miguel Angel; Cisneros Salazar, Guillermo Daniel

2010-01-01

Allergic reactions to insect bites are a global problem, the true incidence and prevalence of morbidity from adverse reactions to mosquito bites are unknown. To describe the adverse reactions to mosquito bites in school-age children of Monterrey, Nuevo Leon. A cross-sectional descriptive study was made via a randomized application of questionnaires to children from public elementary schools in the metropolitan area of Monterrey, Nuevo Leon. A total of 11 public schools randomly selected were included in the study. One thousand questionnaires were submitted, of which 506 fulfilled the inclusion criteria; 55% were females. Seventy-six percent referred adverse reactions to mosquito bites, itching (75%) and rash (72%) being the most frequent ones, in the last 12 months. Adverse reactions to mosquito bites occur frequently. Early detection is important to establish a prompt treatment.

Projected treatment capacity needs in sierra leone.

PubMed

White, Richard A; MacDonald, Emily; de Blasio, Birgitte Freiesleben; Nygård, Karin; Vold, Line; Røttingen, John-Arne

2015-01-30

The ongoing outbreak of Ebola Virus Disease in West Africa requires immediate and sustained input from the international community in order to curb transmission. The CDC has produced a model that indicates that to end the outbreak by pushing the reproductive number below one, 25% of the patients must be placed in an Ebola Treatment Unit (ETC) and 45% must be isolated in community settings in which risk of disease transmission is reduced and safe burials are provided. In order to provide firmer targets for the international response in Sierra Leone, we estimated the national and international personnel and treatment capacity that may be required to reach these percentages. We developed a compartmental SEIR model that was fitted to WHO data and local data allowing the reproductive number to change every 8 weeks to forecast the progression of the EVD epidemic in Sierra Leone. We used the previously estimated 2.5x correction factor estimated by the CDC to correct for underreporting. Number of personnel required to provide treatment for the predicted number of cases was estimated using UNMEER and UN OCHA requests for resources required to meet the CDC target of 70% isolation. As of today (2014-12-04), we estimate that there are 810 (95% CI=646 to 973) EVD active cases in treatment, with an additional 3751 (95% CI=2778 to 4723) EVD cases unreported and untreated. To reach the CDC targets today, we need 1140 (95% CI=894 to 1387) cases in ETCs and 2052 (95% CI=1608 to 2496) at home or in a community setting with a reduced risk for disease transmission. In 28 days (2015-01-01), we will need 1309 (95% CI=804 to 1814) EVD cases in ETCs and 2356 (95% CI=1447 to 3266) EVD cases at reduced risk of transmission. If the current transmission rate is not reduced, up to 3183 personnel in total will be required in 56 days (2015-01-29) to operate ETCs according to our model. The current outbreak will require massive input from the international community in order to curb the

Genetic diversity and evolutionary dynamics of Ebola virus in Sierra Leone.

PubMed

Tong, Yi-Gang; Shi, Wei-Feng; Liu, Di; Qian, Jun; Liang, Long; Bo, Xiao-Chen; Liu, Jun; Ren, Hong-Guang; Fan, Hang; Ni, Ming; Sun, Yang; Jin, Yuan; Teng, Yue; Li, Zhen; Kargbo, David; Dafae, Foday; Kanu, Alex; Chen, Cheng-Chao; Lan, Zhi-Heng; Jiang, Hui; Luo, Yang; Lu, Hui-Jun; Zhang, Xiao-Guang; Yang, Fan; Hu, Yi; Cao, Yu-Xi; Deng, Yong-Qiang; Su, Hao-Xiang; Sun, Yu; Liu, Wen-Sen; Wang, Zhuang; Wang, Cheng-Yu; Bu, Zhao-Yang; Guo, Zhen-Dong; Zhang, Liu-Bo; Nie, Wei-Min; Bai, Chang-Qing; Sun, Chun-Hua; An, Xiao-Ping; Xu, Pei-Song; Zhang, Xiang-Li-Lan; Huang, Yong; Mi, Zhi-Qiang; Yu, Dong; Yao, Hong-Wu; Feng, Yong; Xia, Zhi-Ping; Zheng, Xue-Xing; Yang, Song-Tao; Lu, Bing; Jiang, Jia-Fu; Kargbo, Brima; He, Fu-Chu; Gao, George F; Cao, Wu-Chun

2015-08-06

A novel Ebola virus (EBOV) first identified in March 2014 has infected more than 25,000 people in West Africa, resulting in more than 10,000 deaths. Preliminary analyses of genome sequences of 81 EBOV collected from March to June 2014 from Guinea and Sierra Leone suggest that the 2014 EBOV originated from an independent transmission event from its natural reservoir followed by sustained human-to-human infections. It has been reported that the EBOV genome variation might have an effect on the efficacy of sequence-based virus detection and candidate therapeutics. However, only limited viral information has been available since July 2014, when the outbreak entered a rapid growth phase. Here we describe 175 full-length EBOV genome sequences from five severely stricken districts in Sierra Leone from 28 September to 11 November 2014. We found that the 2014 EBOV has become more phylogenetically and genetically diverse from July to November 2014, characterized by the emergence of multiple novel lineages. The substitution rate for the 2014 EBOV was estimated to be 1.23 × 10(-3) substitutions per site per year (95% highest posterior density interval, 1.04 × 10(-3) to 1.41 × 10(-3) substitutions per site per year), approximating to that observed between previous EBOV outbreaks. The sharp increase in genetic diversity of the 2014 EBOV warrants extensive EBOV surveillance in Sierra Leone, Guinea and Liberia to better understand the viral evolution and transmission dynamics of the ongoing outbreak. These data will facilitate the international efforts to develop vaccines and therapeutics.

Support services for survivors of ebola virus disease - Sierra Leone, 2014.

PubMed

Lee-Kwan, Seung Hee; DeLuca, Nickolas; Adams, Monica; Dalling, Matthew; Drevlow, Elizabeth; Gassama, Gladys; Davies, Tina

2014-12-19

As of December 6, 2014, Sierra Leone reported 6,317 laboratory-confirmed cases of Ebola virus disease (Ebola), the highest number of reported cases in the current West Africa epidemic. The Sierra Leone Ministry of Health and Sanitation reported that as of December 6, 2014, there were 1,181 persons who had survived and were discharged. Survivors from previous Ebola outbreaks have reported major barriers to resuming normal lives after release from treatment, such as emotional distress, health issues, loss of possessions, and difficulty regaining their livelihoods. In August 2014, a knowledge, attitude, and practice survey regarding the Ebola outbreak in Sierra Leone, administered by a consortium of partners that included the Ministry of Health and Sanitation, UNICEF, CDC, and a local nongovernmental organization, Focus 1000, found that 96% of the general population respondents reported some discriminatory attitude towards persons with suspected or known Ebola. Access to increased psychosocial support, provision of goods, and family and community reunification programs might reduce these barriers. Survivors also have unique potential to contribute to the Ebola response, particularly because survivors might have some immunity to the same virus strain. In previous outbreaks, survivors served as burial team members, contact tracers, and community educators promoting messages that seeking treatment improves the chances for survival and that persons who survived Ebola can help their communities. As caregivers in Ebola treatment units, survivors have encouraged patients to stay hydrated and eat and inspired them to believe that they, too, can survive. Survivors regaining livelihood through participation in the response might offset the stigma associated with Ebola.

Phylogenetic Analysis of West Nile Virus, Nuevo Leon State, Mexico

PubMed Central

Blitvich, Bradley J.; Fernández-Salas, Ildefonso; Contreras-Cordero, Juan F.; Loroño-Pino, María A.; Marlenee, Nicole L.; Díaz, Francisco J.; González-Rojas, José I.; Obregón-Martínez, Nelson; Chiu-García, Jorge A.; Black, William C.

2004-01-01

West Nile virus RNA was detected in brain tissue from a horse that died in June 2003 in Nuevo Leon State, Mexico. Nucleotide sequencing and phylogenetic analysis of the premembrane and envelope genes showed that the virus was most closely related to West Nile virus isolates collected in Texas in 2002. PMID:15324558

Why High School Must Go: An Interview with Leon Botstein

ERIC Educational Resources Information Center

Epstein, Robert

2007-01-01

This article presents an interview with Leon Botstein, longtime president of Bard College, as well as music director and conductor of the American and Jerusalem symphony orchestras. Botstein talks about his book entitled "Jefferson's Children: Education and the Promise of American Culture" and his views about teens and high schools in America.…

Stability of Brillouin flow in the presence of slow-wave structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, D. H.; Lau, Y. Y.; Greening, G.

2016-09-15

Including a slow-wave structure (SWS) on the anode in the conventional, planar, and inverted magnetron, we systematically study the linear stability of Brillouin flow, which is the prevalent flow in crossed-field devices. The analytic treatment is fully relativistic and fully electromagnetic, and it incorporates the equilibrium density profile, flow profile, and electric field and magnetic field profiles in the linear stability analysis. Using parameters similar to the University of Michigan's recirculating planar magnetron, the numerical data show that the resonant interaction of the vacuum circuit mode and the corresponding smooth-bore diocotron-like mode is the dominant cause for instability. This resonantmore » interaction is far more important than the intrinsic negative (positive) mass property of electrons in the inverted (conventional) magnetron geometry. It is absent in either the smooth-bore magnetron or under the electrostatic assumption, one or both of which was almost always adopted in prior analytical formulation. This resonant interaction severely restricts the wavenumber for instability to the narrow range in which the cold tube frequency of the SWS is within a few percent of the corresponding smooth bore diocotron-like mode in the Brillouin flow.« less

Collective stimulated Brillouin backscatter

NASA Astrophysics Data System (ADS)

Lushnikov, Pavel; Rose, Harvey

2007-11-01

We develop the statistical theory of linear collective stimulated Brillouin backscatter (CBSBS) in spatially and temporally incoherent laser beam. Instability is collective because it does not depend on the dynamics of isolated hot spots (speckles) of laser intensity, but rather depends on averaged laser beam intensity, optic f/#, and laser coherence time, Tc. CBSBS has a much larger threshold than a classical coherent beam's in long-scale-length high temperature plasma. It is a novel regime in which Tc is too large for applicability of well-known statistical theories (RPA) but Tc must be small enough to suppress single speckle processes such as self-focusing. Even if laser Tc is too large for a priori applicability of our theory, collective forward SBS^1, perhaps enhanced by high Z dopant, and its resultant self-induced Tc reduction, may regain the CBSBS regime. We identified convective and absolute CBSBS regimes. The threshold of convective instability is inside the typical parameter region of NIF designs. Well above incoherent threshold, the coherent instability growth rate is recovered. ^1 P.M. Lushnikov and H.A. Rose, Plasma Physics and Controlled Fusion, 48, 1501 (2006).

Nd:YAP laser pulse compression by three-stage transient stimulated Brillouin and Raman scattering

NASA Astrophysics Data System (ADS)

Kubeček, V.; Hamal, K.; Procházka, I.; Buzelis, R.; Girdauskas, V.; Dementiev, A.

1991-08-01

There is a continuous effort to generate stable, powerful picosecond laser pulses for application in spectroscopy, nonlinear optics and parametric light generation, as well. One of the possible methods is the compression of longer nanosecond laser pulses by stimulated Brillouin and stimulated Raman scattering. The advantages of such a technique, in comparison to the used mode locked picosecond lasers, are as follows: the absence of the active and/or passive mode lockers used to generate a train of picosecond pulses, and the absence of a fast electrooptical shutter used to select a single pulse from a train of pulses. The application of stimulated Brillouin and stimulated Raman scattering permits to generate picosecond pulses in the wavelength regions not covered by mode locked lasers. Of special interest is the wavelength region of 0·8 μm, which may be amplified by the attractive Titanium Sapphire lasers. In this paper we are summarizing our results in theoretical modelling and in real generation of picosecond pulses by means of cascaded stimulated Brillouin and Raman scattering. The models of scattering processes have been investigated. The stable generation of 5, 7, 3 picosecond pulses have been optimized for the wavelengths of 0·8, 0·64 and 0·54 μm, respectively. In all these cases, the pulses exhibited the far field pattern close to Gaussian, with the pulse energy ranging from 0·2 to 1 mJ.

Brillouin Spectroscopy at the GeoForschungsZentrum-Potsdam: Applications in Geosciences and Materials Science

NASA Astrophysics Data System (ADS)

Marquardt, H.; Speziale, S.; Reichmann, H. J.; Schmidt, C.; Schilling, F.

2007-12-01

Knowledge of the elastic properties of earth materials at relevant pressures and temperatures is prerequisite to adequately interpret seismic data and improve our understanding of the composition and mineralogy of the earth's interior. The study of pressure and temperature dependence of acoustic velocity in geo-fluids gives us information about their density with implications for the thermodynamic modelling of diagenetic and metamorphic processes. Furthermore elasticity of synthetic materials is of major interest for several industrial applications. We have recently completed the construction of a new Brillouin System at the GeoForschungsZentrum Potsdam. The new system has been designed to study elasticity of various geological as well as industrial materials at different pressure and temperature conditions. Our Brillouin system consists of a Nd:YVO4 solid state laser operating at a wavelength of 532 nm as light source and a Sandercock-type tandem multipass Fabry-Perot interferometer equipped with a photomultiplier tube for signal detection. Measurements can be performed in 60 or 90 degree symmetric forward scattering or in backscattering geometry. The large positioning system also allows for high temperature measurements in an externally heated diamond anvil cell. We present first results of elasticity measurements both on Earth's materials, such as silicates garnets and oxides, as well as hydroxides and commercially used garnet aluminates, and silicate and borate glasses as proxies for melts. Brillouin scattering has been measured to constrain the density of water-NaCl solutions, for the precise thermodynamic modelling of fluids in metamorphic systems.

Brillouin corrosion expansion sensors for steel reinforced concrete structures using a fiber optic coil winding method.

PubMed

Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

2011-01-01

In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

PubMed Central

Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

2011-01-01

In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. PMID:22346672

Elastic constant and Brillouin oscillations in sputtered vitreous SiO2 thin films

NASA Astrophysics Data System (ADS)

Ogi, H.; Shagawa, T.; Nakamura, N.; Hirao, M.; Odaka, H.; Kihara, N.

2008-10-01

We studied the relationship between elastic constants and microstructure in sputtered vitreous SiO2 thin films using pump-probe picosecond laser ultrasound. The delayed probe light pulse is diffracted by the acoustic wave excited by the pump light pulse, inducing Brillouin oscillations, seen as reflectivity change in the probe pulse, whose frequency can be used to extract the sound velocity and elastic moduli. Theoretical calculations were made to explain the asymmetric response of Brillouin oscillations and to predict the possible error limit of the determined elastic constants. The thin films containing defects exhibited lower elastic constant. A micromechanics modeling was developed to evaluate defect porosity and attenuation caused by scattering was able to predict the defect size. Elastic moduli of the defect-free specimens increased with increasing sputtering power, eventually exceeding the bulk value, and correlated with phonon frequencies, indicating that the decrease in the Si-O-Si bond angle of the tetrahedral structure increased the stiffness.

Tapered fiber based Brillouin random fiber laser and its application for linewidth measurement.

PubMed

Gao, Song; Zhang, Liang; Xu, Yanping; Lu, Ping; Chen, Liang; Bao, Xiaoyi

2016-12-12

A one-end pumping Brillouin random fiber laser (BRFL) based on a 5-km tapered fiber (TF) is demonstrated. The enhanced Rayleigh scattering and the increased power density from tapering in the TF provide good directionality and a high degree of coherent feedback. Both the transmitting and TF enhanced Rayleigh scattered pump lights formed effective bi-direction pumping for the Brillouin gain in the standing cavity configuration in the distributed way as the gain and random feedback in the same fiber. The linewidth of the laser shows ~1.17 kHz while the relative intensity noise (RIN) has been verified to be suppressed comparing with that of the two-end pumping of the standard single mode fiber (SMF). Furthermore, utilizing the proposed laser, a high-resolution (~kHz) linewidth measurement method is demonstrated without long delay fiber (>100km) and extra frequency shifter thanks to the acoustic frequency shift from fiber itself.

Practical way to avoid spurious geometrical contributions in Brillouin light scattering experiments at variable scattering angles.

PubMed

Battistoni, Andrea; Bencivenga, Filippo; Fioretto, Daniele; Masciovecchio, Claudio

2014-10-15

In this Letter, we present a simple method to avoid the well-known spurious contributions in the Brillouin light scattering (BLS) spectrum arising from the finite aperture of collection optics. The method relies on the use of special spatial filters able to select the scattered light with arbitrary precision around a given value of the momentum transfer (Q). We demonstrate the effectiveness of such filters by analyzing the BLS spectra of a reference sample as a function of scattering angle. This practical and inexpensive method could be an extremely useful tool to fully exploit the potentiality of Brillouin acoustic spectroscopy, as it will easily allow for effective Q-variable experiments with unparalleled luminosity and resolution.

Structural terranes and their relationships in Sierra Leone

NASA Astrophysics Data System (ADS)

Williams, Howard R.; Culver, Stephen J.

Sierra Leone, composed mainly of Archaean granite-greenstone terrane, is bounded in the west by a westward dipping zone of intense, ductile, simple shear deformation which produced very fine-grained, high grade rocks. This zone has been interpreted as a possible Archaean suture developed following the collision of the Guyana Shield and the West African Craton. Granulite facies metamorphic supracrustals of the Kasila Group occur to the west of the sheared zone. Marampa Group lower grade metamorphics were thrust eastwards during the collision event. Late Precambrian rifting, well to the east of the mylonite zone and subsequent compression, preserved very low grade to unmetamorphosed Rokel River Group sediments and volcanics. Limited Pan-African tectonic transport of Archaean and late Precambrian material was again toward the east. All structural and stratigraphic units can be traced northward into Guinea where they disappear beneath the Paleozoic sediments of the Bové Basin. To the south, the Kasila Group, the granite-greenstone terrane and the mylonitized zone can be traced into Liberia. The Gibi Mountain Formation of Liberia is probably laterally equivalent to the lower portions of the Rokel River Group. This interpretation of the geology of Sierra Leone differs greatly from that of Guinea where the mylonitized zone, associated with a positive gravity anomaly, has been interpreted as a suture zone resulting from Pan-African continent-continent collision.

A tool and index to assess surgical capacity in low income countries: an initial implementation in Sierra Leone.

PubMed

Groen, Reinou S; Kamara, Thaim B; Dixon-Cole, Richmond; Kwon, Steven; Kingham, T Peter; Kushner, Adam L

2012-08-01

A first step toward improving surgical care in many low and middle income countries is to document the need. To facilitate the collection and analysis of surgical capacity data and measure changes over time, Surgeons OverSeas (SOS) developed a tool and index based on personnel, infrastructure, procedures, equipment, and supplies (PIPES). A follow-up assessment of 10 government hospitals in Sierra Leone was completed 42 months after an initial survey in 2008 using the PIPES tool. An index based on number of operating rooms, personnel, infrastructure, procedures, equipment, and supplies was calculated. An index was also calculated, using the 2008 data for comparison. Most hospitals demonstrated an increased index that correlated with site visits that verified improved conditions. Connaught Hospital in Sierra Leone had the highest score (9.2), consistent with its being the best equipped and staffed Ministry of Health and Sanitation facility. Makeni District Hospital had the greatest increase, from 3.8 to 7.5, consistent with a newly constructed facility. The PIPES tool was easily administered at hospitals in Sierra Leone and an index was found useful. Surgical capacity in Sierra Leone improved between 2008 and 2011, as demonstrated by an increase in the overall PIPES indices.

Medical Officers in Sierra Leone: Surgical Training Opportunities, Challenges and Aspirations.

PubMed

Wilks, Lucy; Leather, Andrew; George, Peter Matthew; Kamara, Thaim Bay

2018-02-05

The critical shortage of human resources for healthcare falls most heavily on sub-Saharan nations such as Sierra Leone, where such workforce deficits have grave impacts on its burden of surgical disease. An important aspect in retention and development of the workforce is training. This study focuses on postgraduate surgical training (formal and short course) and perceptions of opportunities, challenges and aspirations, in a country where more than half of surgical procedures are performed by medical officers. The study presents findings from 12 in-depth semi-structured interviews conducted with medical officers by the primary investigator in Sierra Leone between April and June 2017. Each interview was transcribed alongside an introspective reflexive journal to acknowledge and account for researcher biases. Two interviewees had accessed postgraduate surgical training and 10 (83%) had accessed short course surgically relevant training. The number of short courses accessed grew higher the more recently the medical officers had graduated. Supervision, short length and international standards were the most appreciated aspects of short training courses. Some medical officers perceived the formal postgraduate surgical training programme to be ill-equipped, doubting its credibility. This demotivated some from applying. Training is an essential aspect of developing an adequate surgical workforce. Faith must be restored in the capabilities of Sierra Leone's Ministry of Health and Sanitation to provide adequate and sustainable training. This study advocates for the use of short courses to restore this faith and the expansion of postgraduate surgical training to the districts through developing a regional teaching complex to provide short courses and eventually formal postgraduate training in the future. Copyright © 2018 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Leon Knopoff (1926-2011)

NASA Astrophysics Data System (ADS)

Davis, Paul; Jackson, David; Gilbert, Freeman

2011-06-01

Leon Knopoff died at his home in Sherman Oaks, Calif., on 20 January 2011 at the age of 85. A man of wide-ranging talents, he had the rare distinction of being simultaneously a professor of physics, a professor of geophysics, and a research musicologist at the University of California, Los Angeles (UCLA). As an undergraduate he studied electrical engineering and obtained his Ph.D. in physics and mathematics at the California Institute of Technology (Caltech) in 1949. He was recruited to the Institute of Geophysics (now the Institute of Geophysics and Planetary Physics) at UCLA in 1950 by Louis Slichter, where he became a professor of geophysics in 1957 and of geophysics and physics in 1961. He became a research musicologist in the UCLA Institute of Ethnomusicology soon after it was formed in 1960. Other appointments included faculty positions at Miami University in Ohio (1948-1950) and Caltech (1962-1963) and visiting appointments at Cambridge, Karlsruhe, Harvard, Santiago, Trieste, and Venice.

Distance, accessibility and costs. Decision-making during childbirth in rural Sierra Leone: A qualitative study.

PubMed

Treacy, Laura; Bolkan, Håkon A; Sagbakken, Mette

2018-01-01

Sierra Leone has one of the highest maternal mortality ratios in the world. Efforts to reduce maternal mortality have included initiatives to encourage more women to deliver at health facilities. Despite the introduction of the free health care initiative for pregnant women, many women still continue to deliver at home, with few having access to a skilled birth attendant. In addition, inequalities between rural and urban areas in accessing and utilising health facilities persist. Further insight into how and why women make decisions around childbirth will help guide future plans and initiatives in improving maternal health in Sierra Leone. The objective of this study was to explore the perceptions and decision-making processes of women and their communities during childbirth in rural Sierra Leone. Data were collected through seven focus group discussions and 22 in-depth interviews with recently pregnant women and their community members in two rural villages. Data were analysed using systematic text condensation. Findings revealed that decision-making processes during childbirth are dynamic, intricate and need to be understood within the broader social context that they take place. Factors such as distance and lack of transport, perceived negative behaviour of hospital staff, direct and indirect financial obstacles, as well as the position of women in society all interact and influence how and what decisions are made. Pregnant women face multiple interacting vulnerabilities that influence their healthcare-seeking decisions during pregnancy and childbirth. Future initiatives to improve access and utilisation of safe healthcare services for pregnant women need to be based on adequate knowledge of structural constraints and health inequities that affect women in rural Sierra Leone.

Electromagnetic eigenmodes of collisional and collisionless plasmas and their stability to stimulated Brillouin scattering

NASA Astrophysics Data System (ADS)

Pathak, Vishwa Bandhu; Tripathi, V. K.

2007-02-01

Nonlinear electromagnetic eigenmodes of collisional and collisionless plasmas, when the temporal extent of the modes is longer than the ambipolar diffusion time, have been investigated. The nonlinearity in a collisionless plasma arises through ponderomotive force, whereas in collisional plasmas Ohmic nonlinearity prevails. The mode structure in both cases, representing a balance between the nonlinearity-induced self-convergence and diffraction-induced divergence, closely resembles Gaussian form. The spot size of the mode decreases with the increasing axial amplitude of the laser, attains a minimum, and then rises very gradually. The modes are susceptible to stimulated Brillouin backscattering. The growth rate of the Brillouin process initially increases with mode amplitude, attains a maximum, and then decreases. The reduction in the growth rate is caused by strong electron evacuation from the axial region by the ponderomotive force and thermal pressure gradient force created by nonuniform Ohmic heating.

Investigation of burn effect on skin using simultaneous Raman-Brillouin spectroscopy, and fluorescence microspectroscopy

NASA Astrophysics Data System (ADS)

Coker, Zachary; Meng, Zhaokai; Troyanova-Wood, Maria; Traverso, Andrew; Ballmann, Charles; Petrov, Georgi; Ibey, Bennett L.; Yakovlev, Vladislav

2017-02-01

Burns are thermal injuries that can completely damage or at least compromise the protective function of skin, and affect the ability of tissues to manage moisture. Burn-damaged tissues exhibit lower elasticity than healthy tissues, due to significantly reduced water concentrations and plasma retention. Current methods for determining burn intensity are limited to visual inspection, and potential hospital x-ray examination. We present a unique confocal microscope capable of measuring Raman and Brillouin spectra simultaneously, with concurrent fluorescence investigation from a single spatial location, and demonstrate application by investigating and characterizing the properties of burn-afflicted tissue on chicken skin model. Raman and Brillouin scattering offer complementary information about a material's chemical and mechanical structure, while fluorescence can serve as a useful diagnostic indicator and imaging tool. The developed instrument has the potential for very diverse analytical applications in basic biomedical science and biomedical diagnostics and imaging.

High-power beam steering using phase conjugation through Brillouin-induced four-wave mixing.

PubMed

Jones, D C; Cook, G; Ridley, K D; Scott, A M

1991-10-15

We report an experimental demonstration of a beam-steering concept. A high-reflectivity phase-conjugate mirror is used to steer a high-power phase-conjugate beam using a low-power signal beam. The high reflectivity phase conjugation is achieved using Brillouin-induced four-wave mixing in a cell containing carbon disulfide.

Projected Treatment Capacity Needs in Sierra Leone

PubMed Central

White, Richard A; MacDonald, Emily; de Blasio, Birgitte Freiesleben; Nygård, Karin; Vold, Line; Røttingen, John-Arne

2015-01-01

Background: The ongoing outbreak of Ebola Virus Disease in West Africa requires immediate and sustained input from the international community in order to curb transmission. The CDC has produced a model that indicates that to end the outbreak by pushing the reproductive number below one, 25% of the patients must be placed in an Ebola Treatment Unit (ETC) and 45% must be isolated in community settings in which risk of disease transmission is reduced and safe burials are provided. In order to provide firmer targets for the international response in Sierra Leone, we estimated the national and international personnel and treatment capacity that may be required to reach these percentages. Methods: We developed a compartmental SEIR model that was fitted to WHO data and local data allowing the reproductive number to change every 8 weeks to forecast the progression of the EVD epidemic in Sierra Leone. We used the previously estimated 2.5x correction factor estimated by the CDC to correct for underreporting. Number of personnel required to provide treatment for the predicted number of cases was estimated using UNMEER and UN OCHA requests for resources required to meet the CDC target of 70% isolation. Results: As of today (2014-12-04), we estimate that there are 810 (95% CI=646 to 973) EVD active cases in treatment, with an additional 3751 (95% CI=2778 to 4723) EVD cases unreported and untreated. To reach the CDC targets today, we need 1140 (95% CI=894 to 1387) cases in ETCs and 2052 (95% CI=1608 to 2496) at home or in a community setting with a reduced risk for disease transmission. In 28 days (2015-01-01), we will need 1309 (95% CI=804 to 1814) EVD cases in ETCs and 2356 (95% CI=1447 to 3266) EVD cases at reduced risk of transmission. If the current transmission rate is not reduced, up to 3183 personnel in total will be required in 56 days (2015-01-29) to operate ETCs according to our model. Conclusions: The current outbreak will require massive input from the

Distributed temperature and strain discrimination with stimulated brillouin scattering and rayleigh backscatter in an optical fiber.

PubMed

Zhou, Da-Peng; Li, Wenhai; Chen, Liang; Bao, Xiaoyi

2013-01-31

A distributed optical fiber sensor with the capability of simultaneously measuring temperature and strain is proposed using a large effective area non-zero dispersion shifted fiber (LEAF) with sub-meter spatial resolution. The Brillouin frequency shift is measured using Brillouin optical time-domain analysis (BOTDA) with differential pulse-width pair technique, while the spectrum shift of the Rayleigh backscatter is measured using optical frequency-domain reflectometry (OFDR). These shifts are the functions of both temperature and strain, and can be used as two independent parameters for the discrimination of temperature and strain. A 92 m measurable range with the spatial resolution of 50 cm is demonstrated experimentally, and accuracies of ±1.2 °C in temperature and ±15 με in strain could be achieved.

Le Laboratoire de Mécanique Appliquée Raymond Chaléat a 40 ans !

NASA Astrophysics Data System (ADS)

Comité D'Organisation Du Colloque Ime 2002, Le

2002-12-01

Le LMARC a été créé par Raymond Chaléat dans les locaux de l'École Nationale d'Horlogerie (a présent Lycée Technique Jules Haag).L'équipe de recherche était alors constituée de 2 enseignants-chercheurs (Raymond Chaléat et Gérard Lallement) et d'un technicien (Bernard Prêtre). Les travaux de recherche se situaient naturellement dans le domaine de la chronométrie et en particulier dans la mécanique non linéaire analytique inhérente à la montre en fonctionnement. En effet, Raymond Chaléat fut l'élève, puis le collaborateur du Professeur Jules Haag, mathématicien et mécanicien, lui-même élève de Poincarré.Le LMARC a étendu ses activités avec l'arrivée de Claude Oudet, puis de Claude Oytana à la rhéologie des matériaux solides qui est devenue plus tard l'Équipe Propriétés Mécaniques des Matériaux. En parallèle, G. Lallement a créé une équipe Vibrations devenue à ce jour Dynamique des Structures. À ce jour, le Laboratoire compte plus de 110 personnes dont 40 doctorants.Il a depuis diversifié ses activités avec 3 nouvelles équipes tournées vers la Modélisation et la Mise en Forme des Matériaux, les Micromachines et la Biomécanique et les Mécanismes. Il a su également prendre toute sa place au sein de l'Institut des Microtechniques de Franche-Comté en contribuant à plusieurs thèmes.Notre Laboratoire a été l'un des premiers laboratoires associé au CNRS (4ème) et a toujours été rattaché à l'Université de Franche-Comté (Présidence par C. Oytana de 1996 a 2001) par l'entremise de I'UFR Sciences et Techniques. Il a toujours maintenu des liens forts avec I'ENSMM (École Nationale Supérieure de Mécanique et des Microtechniques) d'une part par ses enseignants-chercheurs et d'autre part deux de ses directeurs, Raymond Chaléat et actuellement Jean-Claude Gelin.En plus de ses relations constantes avec l'industrie régionale, le LMARC a développé des actions contractuelles avec de grands groupes tels que EDF

Characterization of vector stimulated Brillouin scattering gain over wide power range

NASA Astrophysics Data System (ADS)

Li, Yongqian; An, Qi; Li, Xiaojuan; Zhang, Lixin

2017-07-01

The wide range power dependence of vector stimulated Brillouin scattering (SBS) gain is theoretically and experimentally characterized by a mathematical model and measurement system based on the heterodyne pump-Stokes technique. The results show that SBS phase shift is much more tolerant of pump depletion than SBS amplitude gain, hence the performance improvement of the SBS-based distributed sensing system can be achieved by measuring the SBS phase shift spectrum. The discussion about the measured Brillouin spectrum width versus pump power at different Stokes powers reveals that the occurrence of nonnegligible pump depletion imposes a restriction on the determination of pump and Stokes powers in an SBS amplitude gain-based application system. The amplitude gain and phase shift of vector SBS gain increase with the increase of pump power and decrease with the increase of Stokes power, which indicates that the design strategy with smaller Stokes power and higher pump power is reasonable. And the measured center-asymmetry of the SBS phase shift spectrum is mainly caused by the nonlinear refractive index, which puts a limitation on the maximum pump power. The obtained results can provide a useful basis for the optimal design of practical vector SBS gain-based application systems.

Water quality associated public health risk in Bo, Sierra Leone.

PubMed

Jimmy, David H; Sundufu, Abu J; Malanoski, Anthony P; Jacobsen, Kathryn H; Ansumana, Rashid; Leski, Tomasz A; Bangura, Umaru; Bockarie, Alfred S; Tejan, Edries; Lin, Baochuan; Stenger, David A

2013-01-01

Human health depends on reliable access to safe drinking water, but in many developing countries only a limited number of wells and boreholes are available. Many of these water resources are contaminated with biological or chemical pollutants. The goal of this study was to examine water access and quality in urban Bo, Sierra Leone. A health census and community mapping project in one neighborhood in Bo identified the 36 water sources used by the community. A water sample was taken from each water source and tested for a variety of microbiological and physicochemical substances. Only 38.9% of the water sources met World Health Organization (WHO) microbial safety requirements based on fecal coliform levels. Physiochemical analysis indicated that the majority (91.7%) of the water sources met the requirements set by the WHO. In combination, 25% of these water resources met safe drinking water criteria. No variables associated with wells were statistically significant predictors of contamination. This study indicated that fecal contamination is the greatest health risk associated with drinking water. There is a need to raise hygiene awareness and implement inexpensive methods to reduce fecal contamination and improve drinking water safety in Bo, Sierra Leone.

Brillouin-scattering study of liquid-glass transitions in ternary mixtures of water, trehalose, and an ionic liquid

NASA Astrophysics Data System (ADS)

Takayama, Haruki; Shibata, Tomohiko; Ishii, Takahiro; Kojima, Seiji

2013-04-01

Ternary mixtures of water, sugar, and ionic liquid have been studied as new candidates for bioprotectants. To clarify the elastic properties and relaxation dynamics of the supercooled liquid and glassy states at low temperatures, the liquid-glass transitions were investigated by using a micro-Brillouin-scattering technique. The refractive index was measured accurately as a function of content and temperature to determine the sound velocity and the attenuation from Brillouin frequency shift and peak width. The relaxation times of structural relaxations related to liquidglass transitions were determined as functions of temperature. The Meyer-Neldel rule was found to hold for the activation energy and the prefactor of the Arrhenius law for the relaxation time.

Brillouin distributed temperature sensing system for monitoring of submarine export cables of off-shore wind farms

NASA Astrophysics Data System (ADS)

Marx, Benjamin; Rath, Alexander; Kolm, Frederick; Schröder, Andreas; Buntebarth, Christian; Dreß, Albrecht; Hill, Wieland

2016-05-01

For high-voltage cables, the maximum temperature of the insulation must never be exceeded at any location and at any load condition. The local temperatures depend not only on the cable design and load history, but also on the local thermal environment of the cable. Therefore, distributed temperature monitoring of high-voltage cables is essential to ensure the integrity of the cable at high load. Especially, the load of the export cables of wind farms varies strongly in dependence on weather conditions. In this field study, we demonstrate the measurement performance of a new, robust Brillouin distributed temperature sensing system (Brillouin-DTS). The system is based on spontaneous Brillouin scattering and does not require a fibre loop. This is essential for long submarine high-voltage cables, where normally no loop can be formed in the seabed. It is completely passively cooled and does not contain any moving or wearing parts. The instrument is dedicated for use in industrial and other rough environments. With a measuring time below 10 min, the temperature resolution is better than 1 °C for distances up to 50 km. In the field study, the submarine export cable of an off-shore wind farm has been monitored. The temperature profile of the export cable shows several hot spots, mostly located at cable joints, and also several cold spots.

Optimization of the Brillouin operator on the KNL architecture

NASA Astrophysics Data System (ADS)

Dürr, Stephan

2018-03-01

Experiences with optimizing the matrix-times-vector application of the Brillouin operator on the Intel KNL processor are reported. Without adjustments to the memory layout, performance figures of 360 Gflop/s in single and 270 Gflop/s in double precision are observed. This is with Nc = 3 colors, Nv = 12 right-hand-sides, Nthr = 256 threads, on lattices of size 323 × 64, using exclusively OMP pragmas. Interestingly, the same routine performs quite well on Intel Core i7 architectures, too. Some observations on the much harderWilson fermion matrix-times-vector optimization problem are added.

Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean

NASA Astrophysics Data System (ADS)

Rudolf, Andreas; Walther, Thomas

2014-05-01

We report on the successful laboratory demonstration of a real-time lidar system to remotely measure temperature profiles in water. In the near future, it is intended to be operated from a mobile platform, e.g., a helicopter or vessel, in order to precisely determine the temperature of the surface mixed layer of the ocean with high spatial resolution. The working principle relies on the active generation and detection of spontaneous Brillouin scattering. The light source consists of a frequency-doubled fiber-amplified external cavity diode laser and provides high-energy, Fourier transform-limited laser pulses in the green spectral range. The detector is based on an atomic edge filter and allows the challenging extraction of the temperature information from the Brillouin scattered light. In the lab environment, depending on the amount of averaging, water temperatures were resolved with a mean accuracy of up to 0.07°C and a spatial resolution of 1 m, proving the feasibility and the large potential of the overall system.

Contraception determinants in youths of Sierra Leone are largely behavioral.

PubMed

Labat, Aline; Medina, Marta; Elhassein, Mohammed; Karim, Afrina; Jalloh, Mohammad B; Dramaix, Michèle; Zhang, Wei-Hong; Alexander, Sophie; Dickson, Kim E

2018-04-19

Sexual initiation occurs early in Sierra Leone. This study aims to analyze the determinants of condom and/or contraceptive use among a representative sample of young persons (10 to 24 years) in Sierra Leone. This is a secondary analysis of data from a study conducted to monitor the implementation of a UNFPA package of interventions directed to improve SRH in young people of Sierra Leone. This assessment was conducted in 2016 at the end of the Ebola outbreak. In consequence, determinants linked to healthy lifestyle behaviors and UNFPA interventions were explored in addition to the usual determinants: socio demographic and sexual lifestyle. This study is a household quantitative survey with open ended questions used to illustrate and complete the analysis. A total of 1409 young people were interviewed: of these, 216 boys and 381 girls were sexually active. Those who were pregnant or wished for pregnancy were excluded, leaving 194 boys and 268 girls for the analysis of determinants. The proportion of young people using neither condom nor other contraception at their last sexual intercourse in the whole sample was 40.5% and there was no statistically significant difference between boys and girls (42.3 vs 39.2; P = 0.504). Determinants were assessed and, after multivariable analysis, results differed between boys and girls and showed the importance of behavioral aspects. Four determinants were common to boys and girls: literacy, distance, negotiation capacity and hand washing. However, the distance factor for girls was to the health facility and for boys it was to school. Three more determinants remained in the boy's model: sleeping under a bednet, number of sexual partners and knowledge of contraceptive methods. Opinions about condoms and contraception revealed important barriers; opposition to contraceptive use was the main reason for non-use for both boys and girls, while lack of access was an important reason for boys. There is a need to reach out to the 40% of

Thin-film optoacoustic transducers for subcellular Brillouin oscillation imaging of individual biological cells.

PubMed

Pérez-Cota, Fernando; Smith, Richard J; Moradi, Emilia; Marques, Leonel; Webb, Kevin F; Clark, Matt

2015-10-01

At low frequencies ultrasound is a valuable tool to mechanically characterize and image biological tissues. There is much interest in using high-frequency ultrasound to investigate single cells. Mechanical characterization of vegetal and biological cells by measurement of Brillouin oscillations has been demonstrated using ultrasound in the GHz range. This paper presents a method to extend this technique from the previously reported single-point measurements and line scans into a high-resolution acoustic imaging tool. Our technique uses a three-layered metal-dielectric-metal film as a transducer to launch acoustic waves into the cell we want to study. The design of this transducer and measuring system is optimized to overcome the vulnerability of a cell to the exposure of laser light and heat without sacrificing the signal-to-noise ratio. The transducer substrate shields the cell from the laser radiation, efficiently generates acoustic waves, facilitates optical detection in transmission, and aids with heat dissipation away from the cell. This paper discusses the design of the transducers and instrumentation and presents Brillouin frequency images on phantom, fixed, and living cells.

List of Organizing Committees and Conference Programme

NASA Astrophysics Data System (ADS)

2012-03-01

Organizers Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH Romanian Neutron Scattering Society Sponsors Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH Comenius University in Bratislava, Slovakia Institute of Macromolecular Chemistry AS CR, Czech Republic Programme Committee Valentin Gordely (chairman)Joint Institute for Nuclear Research, Russia Heinrich StuhrmannGermany Jose TeixeiraLaboratoire Leon Brillouin, France Pavel ApelJoint Institute for Nuclear Research, Russia Pavol BalgavyComenius University in Bratislava, Slovakia Alexander BelushkinJoint Institute for Nuclear Research, Russia Georg BueldtInstitute of Structural Biology and Biophysics (ISB), Germany Leonid BulavinTaras Shevchenko National University of Kyiv, Ukraine Emil BurzoBabes-Bolyai University, Romania Vadim CherezovThe Scripps Research Institute, Department of Molecular Biology, USA Ion IonitaRomanian Society of Neutron Scattering, Romania Alexei KhokhlovMoscow State University, Russia Aziz MuzafarovInstitute of Synthetic Polymeric Materials, Russian Academy of Sciences, Russia Alexander OzerinInstitute of Synthetic Polymeric Materials, Russian Academy of Sciences, Russia Gerard PepyResearch Institute for Solid State Physics and Optics, Hungary Josef PlestilInstitute of Macromolecular Chemistry CAS, Czech Republic Aurel RadulescuJuelich Centre for Neutron Science JCNS, Germany Maria BalasoiuJoint Institute for Nuclear Research, Russia Alexander KuklinJoint Institute for Nuclear Research, Russia Local Organizing Committee Alexander Kuklin - Chairman Maria Balasoiu - Co-chairman Tatiana Murugova - Secretary Natalia Malysheva Natalia Dokalenko Julia Gorshkova Andrey Rogachev Oleksandr Ivankov Dmitry Soloviev Lilia Anghel Erhan Raul The PDF also contains the Conference Programme.

Dynamical Chern-Simons Theory in the Brillouin Zone

NASA Astrophysics Data System (ADS)

Lian, Biao; Vafa, Cumrun; Vafa, Farzan; Zhang, Shou-Cheng

Berry connection is conventionally defined as a static gauge field in the Brillouin zone. Here we show that for three-dimensional (3d) time-reversal invariant superconductors, a generalized Berry gauge field behaves as a dynamical fluctuating field of a Chern-Simons gauge theory. The gapless nodal lines in the momentum space play the role of Wilson loop observables, while their linking and knot invariants modify the gravitational theta angle. This angle induces a topological gravitomagnetoelectric effect where a temperature gradient induces a rotational energy flow. We also show how topological strings may be realized in the 6 dimensional phase space, where the physical space defects play the role of topological D-branes.

Prevalence of Autism Spectrum Disorders in Guanajuato, Mexico: The Leon Survey

ERIC Educational Resources Information Center

Fombonne, Eric; Marcin, Carlos; Manero, Ana Cecilia; Bruno, Ruth; Diaz, Christian; Villalobos, Michele; Ramsay, Katrina; Nealy, Benjamin

2016-01-01

There are no epidemiological data on autism for Mexico. This study was conducted to generate a first estimate of ASD prevalence in Mexico. We surveyed children age eight in Leon (Guanajuato). The sample was stratified in two strata: (1) children having special education and medical records (SEMR; N = 432) and (2) children attending regular schools…

[Leon Daraszkiewicz and his monograph on hebephrenia].

PubMed

Marcinowski, Filip

2012-01-01

Leon Daraszkiewicz (1866-1931) was a Polish psychiatrist, a pupil and co-worker of E. Kraepelin and V. Tsiz on the University of Dorpat (now Tartu, Estonia), the author of highly regarded monograph on hebephrenia (1891). In his work on the basis of over 20 case histories, he described a natural history of hebephrenia and his own views on its aetiology and prognosis. Hebephrenia as described by Daraszkiewicz, served as a clinical model for the Kraepelinian concept of dementia praecox. In the article, the life and career of Daraszkiewicz is covered, with particular emphasis on the role of his doctoral dissertation on hebephrenia in the history of the concept of schizophrenia.

Double peak-induced distance error in short-time-Fourier-transform-Brillouin optical time domain reflectometers event detection and the recovery method.

PubMed

Yu, Yifei; Luo, Linqing; Li, Bo; Guo, Linfeng; Yan, Jize; Soga, Kenichi

2015-10-01

The measured distance error caused by double peaks in the BOTDRs (Brillouin optical time domain reflectometers) system is a kind of Brillouin scattering spectrum (BSS) deformation, discussed and simulated for the first time in the paper, to the best of the authors' knowledge. Double peak, as a kind of Brillouin spectrum deformation, is important in the enhancement of spatial resolution, measurement accuracy, and crack detection. Due to the variances of the peak powers of the BSS along the fiber, the measured starting point of a step-shape frequency transition region is shifted and results in distance errors. Zero-padded short-time-Fourier-transform (STFT) can restore the transition-induced double peaks in the asymmetric and deformed BSS, thus offering more accurate and quicker measurements than the conventional Lorentz-fitting method. The recovering method based on the double-peak detection and corresponding BSS deformation can be applied to calculate the real starting point, which can improve the distance accuracy of the STFT-based BOTDR system.

Brillouin light scattering on Fe/Cr/Fe thin-film sandwiches

NASA Astrophysics Data System (ADS)

Kabos, P.; Patton, C. E.; Dima, M. O.; Church, D. B.; Stamps, R. L.; Camley, R. E.

1994-04-01

The aim of this work is to perform Brillouin light scattering measurements of the field and wave-vector dependencies of the frequencies of the fundamental magnetic excitations in Fe/Cr/Fe thin film sandwiches with antiferromagnetically coupled magnetic layers, correlate these results with magnetization versus field data on such films, and compare the observed dependencies with theory for low-wave number spin-wave modes in sandwich films. The measurements were made for the in-plane static magnetic field H along the crystallographic and directions, with the in-plane wave vector k always perpendicular to H.

Active frequency matching in stimulated Brillouin amplification for production of a 2.4  J, 200  ps laser pulse.

PubMed

Yuan, Hang; Wang, Yulei; Lu, Zhiwei; Zheng, Zhenxing

2018-02-01

A frequency matching Brillouin amplification in high-power solid-state laser systems is proposed. The energy extraction efficiency could be maintained at a high level in a non-collinear Brillouin amplification structure using an exact Stokes frequency shift. Laser pulses having a width of 200 ps and energy of 2.4 J were produced. This method can be used to transfer energy from a long pulse to a short pulse through a high-power solid-state laser system.

Tertiary carbonate-dissolution cycles on the Sierra Leone Rise, eastern equatorial Atlantic Ocean

USGS Publications Warehouse

Dean, W.E.; Gardner, J.V.; Cepek, P.

1981-01-01

Most of the Tertiary section on Sierra Leone Rise off northwest Africa consists of chalk, marl, and limestone that show cyclic alterations of clay-rich and clay-poor beds about 20-60 cm thick. On the basis of biostratigraphic accumulation rates, the cycles in Oligocene and Miocene chalk have periods which average about 44,000 years, and those in Eocene siliceous limestone have periods of 4000-27,000 years. Several sections were sampled in detail to further define the cycles in terms of content of CaCO3, clay minerals, and relative abundances of calcareous nannofossils. Extending information gained by analyses of Pleistocene cores from the continental margin of northwest Africa to the Tertiary cycles on Sierra Leone Rise, both dilution by noncarbonate material and dissolution of CaCO3 could have contributed to the observed relative variations in clay and CaCO3. However, dissolution of CaCO3 as the main cause of the carbonate-clay cycles on the Sierra Leone Rise, rather than dilution by clay, is suggested by the large amount of change (several thousand percent) in terrigenous influx required to produce the observed variations in amount of clay and by the marked increase in abundance of dissolution-resistant discoasters relative to more easily dissolved coccoliths in low-carbonate parts of cycles. The main cause of dissolution of CaCO3 was shoaling of the carbonate compensation depth (CCD) during the early Neogene and climatically induced fluctuations in the thickness of Antarctic Bottom Water. ?? 1981.

A Brillouin smart FRP material and a strain data post processing software for structural health monitoring through laboratory testing and field application on a highway bridge

NASA Astrophysics Data System (ADS)

Bastianini, Filippo; Matta, Fabio; Galati, Nestore; Nanni, Antonio

2005-05-01

Strain and temperature sensing obtained through frequency shift evaluation of Brillouin scattered light is a technology that seems extremely promising for Structural Health Monitoring (SHM). Due to the intrinsic distributed sensing capability, Brillouin can measure the deformation of any individual segment of huge lengths of inexpensive single-mode fiber. In addition, Brillouin retains other typical advantages of Fiber Optic Sensors (FOS), such as harsh environment durability and interference rejection. Despite these advantages, the diffusion of Brillouin for SHM is constrained by different factors, such as the high equipment cost, the commercial unavailability of specific SHM oriented fiber products and even some prejudices on the required sensitivity performances. In the present work, a complete SHM pilot application was developed, installed and successfully operated during a diagnostic load test on the High Performance Steel (HPS) bridge A6358 located at the Lake of the Ozarks (Miller County, MO, USA). Four out of five girders were extensively instrumented with a "smart" Glass Fiber Reinforced Polymer (GFRP) tape having embedded fibers for strain sensing and thermal compensation. Data collected during a diagnostic load test were elaborated through a specific post-processing software, and the strain profiles retrieved were compared to traditional strain gauges and theoretical results based on the AASHTO LRFD Bridge Design Specifications for structural assessment purposes. The excellent results obtained confirm the effectiveness of Brillouin SHM systems for the monitoring of real applications.

Stimulated Brillouin scattering in highly birefringent multimode tapered chalcogenide photonic crystal fiber for distributed optical sensors (Retraction Notice)

NASA Astrophysics Data System (ADS)

Baili, Amira; Cherif, Rim; Zghal, Mourad

2016-09-01

This paper, originally published on September 15, 2016, was retracted from the SPIE Digital Library on October 5, 2016, due to a high degree of similarity between specific portions of the text of the paper to the following publications: J. Tchahame, J. Beugnot, A. Kudlinski, and T. Sylvestre, "Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber," Opt. Lett. 40, 4281-4284 (2015). doi: 10.1364/OL.40.004281 W. W. Ke, X. J. Wang and X. Tang, "Stimulated Brillouin Scattering Model in Multi-Mode Fiber Lasers," in IEEE Journal of Selected Topics in Quantum Electronics, vol. 20, no. 5, pp. 305-314, Sept.-Oct. 2014. doi: 10.1109/JSTQE.2014.2303256.

Detection of 2-mm-long strained section in silica fiber using slope-assisted Brillouin optical correlation-domain reflectometry

NASA Astrophysics Data System (ADS)

Lee, Heeyoung; Mizuno, Yosuke; Nakamura, Kentaro

2018-02-01

Slope-assisted Brillouin optical correlation-domain reflectometry is a single-end-access distributed Brillouin sensing technique with high spatial resolution and high-speed operation. We have recently discovered its unique feature, that is, strained or heated sections even shorter than nominal resolution can be detected, but its detailed characterization has not been carried out. Here, after experimentally characterizing this “beyond-nominal-resolution” effect, we show its usefulness by demonstrating the detection of a 2-mm-long strained section along a silica fiber. We also demonstrate the detection of a 5-mm-long heated section along a polymer optical fiber. The lengths of these detected sections are smaller than those of the other demonstrations reported so far.

Socio-Ecological Factors Affecting Pregnant Women's Anemia Status in Freetown, Sierra Leone

ERIC Educational Resources Information Center

M'Cormack, Fredanna; Drolet, Judy

2012-01-01

Background: Sierra Leone has high maternal mortality. Socio-ecological factors are considered contributing factors to this high mortality. Anemia is considered to be a direct cause of 4% of maternal deaths and an indirect cause of 20-40% of maternal deaths. Purpose: The current study explores socio-ecological contributing factors to the anemia…

The effect of signal to noise ratio on accuracy of temperature measurements for Brillouin lidar in water

NASA Astrophysics Data System (ADS)

Liang, Kun; Niu, Qunjie; Wu, Xiangkui; Xu, Jiaqi; Peng, Li; Zhou, Bo

2017-09-01

A lidar system with Fabry-Pérot etalon and an intensified charge coupled device can be used to obtain the scattering spectrum of the ocean and retrieve oceanic temperature profiles. However, the spectrum would be polluted by noise and result in a measurement error. To analyze the effect of signal to noise ratio (SNR) on the accuracy of measurements for Brillouin lidar in water, the theory model and characteristics of SNR are researched. The noise spectrums with different SNR are repetitiously measured based on simulation and experiment. The results show that accuracy is related to SNR, and considering the balance of time consumption and quality, the average of five measurements is adapted for real remote sensing under the pulse laser conditions of wavelength 532 nm, pulse energy 650 mJ, repetition rate 10 Hz, pulse width 8 ns and linewidth 0.003 cm-1 (90 MHz). Measuring with the Brillouin linewidth has a better accuracy at a lower temperature (<15 °C), while measuring with the Brillouin shift is a more appropriate method at a higher temperature (>15 °C), based on the classical retrieval model we adopt. The experimental results show that the temperature error is 0.71 °C and 0.06 °C based on shift and linewidth respectively when the image SNR is at the range of 3.2 dB-3.9 dB.

Improving access to surgery in a developing country: experience from a surgical collaboration in Sierra Leone.

PubMed

Kushner, Adam L; Kamara, Thaim B; Groen, Reinou S; Fadlu-Deen, Betsy D; Doah, Kisito S; Kingham, T Peter

2010-01-01

Although surgery is increasingly recognized as an essential component of primary health care, there has been little documentation of surgical programs in low- and middle-income countries. Surgeons OverSeas (SOS) is a New York-based organization with a mission to save lives in developing countries by improving surgical care. This article highlights the surgical program in Sierra Leone as a possible model to improve access to surgery. An SOS team conducted a needs assessment of surgical capacity in Sierra Leone in February 2008. Interventions were then developed and programs were implemented. A follow-up assessment was conducted in December 2009, which included interviews of key Sierra Leone hospital personnel and a review of operating room log books. Based on an initial needs assessment, a program was developed that included training, salary support, and the provision of surgical supplies and equipment. Two 3-day workshops were conducted for a total of 44 health workers, salary support given to over 100 staff, and 2 containers of supplies and equipment were donated. Access to surgery, as measured by the number of major operations at Connaught Hospital, increased from 460 cases in 2007 to 768 cases in 2009. The SOS program in Sierra Leone highlights a method for improving access to surgery that incorporates an initial needs assessment with minimal external support and local staff collaboration. The program functions as a catalyst by providing training, salary support, and supplies. The beneficial results of the program can then be used to advocate for additional resources for surgery from policy makers. This model could be beneficial in other resource-poor countries in which improved access to surgery is desired. Copyright 2010 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Optimization of interaction conditions for efficient short laser pulse amplification by stimulated Brillouin scattering in the strongly coupled regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiaramello, M.; Riconda, C.; Amiranoff, F.

Plasma amplification of low energy, a short (∼100–500 fs) laser pulse by an energetic long (∼10 ps) pulse via strong coupling Stimulated Brillouin Backscattering is investigated with an extensive analysis of one-dimensional particle-in-cell simulations. Parameters relevant to nowadays experimental conditions are investigated. The obtained seed pulse spectra are analyzed as a function of the interaction conditions such as plasma profile, pulses delay, and seed or pulse duration. The factors affecting the amount of energy transferred are determined, and the competition between Brillouin-based amplification and parasitic Raman backscattering is analyzed, leading to the optimization of the interaction conditions.

Comprehensive Yet Scalable Health Information Systems for Low Resource Settings: A Collaborative Effort in Sierra Leone

PubMed Central

Braa, Jørn; Kanter, Andrew S.; Lesh, Neal; Crichton, Ryan; Jolliffe, Bob; Sæbø, Johan; Kossi, Edem; Seebregts, Christopher J.

2010-01-01

We address the problem of how to integrate health information systems in low-income African countries in which technical infrastructure and human resources vary wildly within countries. We describe a set of tools to meet the needs of different service areas including managing aggregate indicators, patient level record systems, and mobile tools for community outreach. We present the case of Sierra Leone and use this case to motivate and illustrate an architecture that allows us to provide services at each level of the health system (national, regional, facility and community) and provide different configurations of the tools as appropriate for the individual area. Finally, we present a, collaborative implementation of this approach in Sierra Leone. PMID:21347003

Habitat preferences of butterflies in the Bumbuna Forest, Northern Sierra Leone.

PubMed

Sundufu, Abu James; Dumbuya, Rashida

2008-01-01

The habitat preferences of the butterfly fauna were studied in the Bumbuna Forest Reserve in northern Sierra Leone. The intact forest reserve and a secondary forest regrowth, disturbed as a result of slash-and-burn agriculture, were compared to savanna habitats. Of the 290 specimens collected, 195 butterfly species were included, of which significant proportion were Nymphalidae. Of the 147 forest species, 111 (75.5%) showed preferences for the forest habitats, while 70 (47.6%) and 34 (23.1%) preferred disturbed and savannah habitats, respectively. Numerically, a comparable proportion of savannah species were recorded in the 18 disturbed (73.9%) and 16 savannah habitats (63.2%). Accumulated species richness and diversity indices were lower in the disturbed habitats compared to the forest reserve, but lowest in the savanna habitats. However, a large proportion of forest species, especially those with either a more restricted geographic range or species for which no information on geographic distribution was available, were exclusively captured in the forest patches. The survey indicated the presence of a rich butterfly fauna, which should be systematically collected for further research and study in order to build a good taxonomic database for Sierra Leone.

Habitat Preferences of Butterflies in the Bumbuna Forest, Northern Sierra Leone

PubMed Central

Sundufu, Abu James; Dumbuya, Rashida

2008-01-01

The habitat preferences of the butterfly fauna were studied in the Bumbuna Forest Reserve in northern Sierra Leone. The intact forest reserve and a secondary forest regrowth, disturbed as a result of slash-and-burn agriculture, were compared to savanna habitats. Of the 290 specimens collected, 195 butterfly species were included, of which significant proportion were Nymphalidae. Of the 147 forest species, 111 (75.5%) showed preferences for the forest habitats, while 70 (47.6%) and 34 (23.1%) preferred disturbed and savannah habitats, respectively. Numerically, a comparable proportion of savannah species were recorded in the 18 disturbed (73.9%) and 16 savannah habitats (63.2%). Accumulated species richness and diversity indices were lower in the disturbed habitats compared to the forest reserve, but lowest in the savanna habitats. However, a large proportion of forest species, especially those with either a more restricted geographic range or species for which no information on geographic distribution was available, were exclusively captured in the forest patches. The survey indicated the presence of a rich butterfly fauna, which should be systematically collected for further research and study in order to build a good taxonomic database for Sierra Leone. PMID:20302525

Child mental health in Sierra Leone: a survey and exploratory qualitative study.

PubMed

Yoder, Hélène N C; Tol, Wietse A; Reis, Ria; de Jong, Joop T V M

2016-01-01

This study complements the growing amount of research on the psychosocial impact of war on children in Sierra Leone by examining local perceptions of child mental health, formal and informal care systems, help-seeking behaviour and stigma. The study combined: (1) a nationwide survey of mental health care providers, with (2) exploratory qualitative research among service users and providers and other stakeholders concerned with child and adolescent mental health, with a particular emphasis on local explanations and stigma. Formal mental health care services are extremely limited resulting in an estimated treatment gap of over 99.8 %. Local explanations of child mental health problems in Sierra Leone are commonly spiritual or supernatural in nature, and associated with help-seeking from traditional healers or religious institutions. There is a considerable amount of stigma related to mental disorders, which affects children, their caregivers and service providers, and may lead to discrimination and abuse. Child and Adolescent Mental Health (CAMH) care development in Sierra Leone should cater to the long-term structural effects of war-violence and an Ebola epidemic. Priorities for development include: (1) the strengthening of legal structures and the development of relevant policies that strengthen the health system and specifically include children and adolescents, (2) a clearer local distinction between children with psychiatric, neurological, developmental or psychosocial problems and subsequent channelling into appropriate services (3) supplementary CAMH training for a range of professionals working with children across various sectors, (4) specialist training in CAMH, (5) integration of CAMH care into primary health care, education and the social welfare system, (6) further research on local explanations of child mental disorders and the effect they have on the well-being of the child, and (7) a careful consideration of the role of religious healers as care

Post-Ebola Syndrome, Sierra Leone.

PubMed

Scott, Janet T; Sesay, Foday R; Massaquoi, Thomas A; Idriss, Baimba R; Sahr, Foday; Semple, Malcolm G

2016-04-01

Thousands of persons have survived Ebola virus disease. Almost all survivors describe symptoms that persist or develop after hospital discharge. A cross-sectional survey of the symptoms of all survivors from the Ebola treatment unit (ETU) at 34th Regimental Military Hospital, Freetown, Sierra Leone (MH34), was conducted after discharge at their initial follow-up appointment within 3 weeks after their second negative PCR result. From its opening on December 1, 2014, through March 31, 2015, the MH34 ETU treated 84 persons (8-70 years of age) with PCR-confirmed Ebola virus disease, of whom 44 survived. Survivors reported musculoskeletal pain (70%), headache (48%), and ocular problems (14%). Those who reported headache had had lower admission cycle threshold Ebola PCR than did those who did not (p<0.03). This complete survivor cohort from 1 ETU enables analysis of the proportion of symptoms of post-Ebola syndrome. The Ebola epidemic is waning, but the effects of the disease will remain.

Ebola Virus Epidemiology, Transmission, and Evolution during Seven Months in Sierra Leone

PubMed Central

Park, Daniel J.; Dudas, Gytis; Wohl, Shirlee; Goba, Augustine; Whitmer, Shannon L.M.; Andersen, Kristian G.; Sealfon, Rachel S.; Ladner, Jason T.; Kugelman, Jeffrey R.; Matranga, Christian B.; Winnicki, Sarah M.; Qu, James; Gire, Stephen K.; Gladden-Young, Adrianne; Jalloh, Simbirie; Nosamiefan, Dolo; Yozwiak, Nathan L.; Moses, Lina M.; Jiang, Pan-Pan; Lin, Aaron E.; Schaffner, Stephen F.; Bird, Brian; Towner, Jonathan; Mamoh, Mambu; Gbakie, Michael; Kanneh, Lansana; Kargbo, David; Massally, James L.B.; Kamara, Fatima K.; Konuwa, Edwin; Sellu, Josephine; Jalloh, Abdul A.; Mustapha, Ibrahim; Foday, Momoh; Yillah, Mohamed; Erickson, Bobbie R.; Sealy, Tara; Blau, Dianna; Paddock, Christopher; Brault, Aaron; Amman, Brian; Basile, Jane; Bearden, Scott; Belser, Jessica; Bergeron, Eric; Campbell, Shelley; Chakrabarti, Ayan; Dodd, Kimberly; Flint, Mike; Gibbons, Aridth; Goodman, Christin; Klena, John; McMullan, Laura; Morgan, Laura; Russell, Brandy; Salzer, Johanna; Sanchez, Angela; Wang, David; Jungreis, Irwin; Tomkins-Tinch, Christopher; Kislyuk, Andrey; Lin, Michael F.; Chapman, Sinead; MacInnis, Bronwyn; Matthews, Ashley; Bochicchio, James; Hensley, Lisa E.; Kuhn, Jens H.; Nusbaum, Chad; Schieffelin, John S.; Birren, Bruce W.; Forget, Marc; Nichol, Stuart T.; Palacios, Gustavo F.; Ndiaye, Daouda; Happi, Christian; Gevao, Sahr M.; Vandi, Mohamed A.; Kargbo, Brima; Holmes, Edward C.; Bedford, Trevor; Gnirke, Andreas; Ströher, Ute; Rambaut, Andrew; Garry, Robert F.; Sabeti, Pardis C.

2015-01-01

Summary The 2013–2015 Ebola virus disease (EVD) epidemic is caused by the Makona variant of Ebola virus (EBOV). Early in the epidemic, genome sequencing provided insights into virus evolution and transmission and offered important information for outbreak response. Here, we analyze sequences from 232 patients sampled over 7 months in Sierra Leone, along with 86 previously released genomes from earlier in the epidemic. We confirm sustained human-to-human transmission within Sierra Leone and find no evidence for import or export of EBOV across national borders after its initial introduction. Using high-depth replicate sequencing, we observe both host-to-host transmission and recurrent emergence of intrahost genetic variants. We trace the increasing impact of purifying selection in suppressing the accumulation of nonsynonymous mutations over time. Finally, we note changes in the mucin-like domain of EBOV glycoprotein that merit further investigation. These findings clarify the movement of EBOV within the region and describe viral evolution during prolonged human-to-human transmission. PMID:26091036

Brillouin Frequency Shift of Fiber Distributed Sensors Extracted from Noisy Signals by Quadratic Fitting.

PubMed

Zheng, Hanrong; Fang, Zujie; Wang, Zhaoyong; Lu, Bin; Cao, Yulong; Ye, Qing; Qu, Ronghui; Cai, Haiwen

2018-01-31

It is a basic task in Brillouin distributed fiber sensors to extract the peak frequency of the scattering spectrum, since the peak frequency shift gives information on the fiber temperature and strain changes. Because of high-level noise, quadratic fitting is often used in the data processing. Formulas of the dependence of the minimum detectable Brillouin frequency shift (BFS) on the signal-to-noise ratio (SNR) and frequency step have been presented in publications, but in different expressions. A detailed deduction of new formulas of BFS variance and its average is given in this paper, showing especially their dependences on the data range used in fitting, including its length and its center respective to the real spectral peak. The theoretical analyses are experimentally verified. It is shown that the center of the data range has a direct impact on the accuracy of the extracted BFS. We propose and demonstrate an iterative fitting method to mitigate such effects and improve the accuracy of BFS measurement. The different expressions of BFS variances presented in previous papers are explained and discussed.

Clinical illness and outcomes in patients with Ebola in Sierra Leone.

PubMed

Schieffelin, John S; Shaffer, Jeffrey G; Goba, Augustine; Gbakie, Michael; Gire, Stephen K; Colubri, Andres; Sealfon, Rachel S G; Kanneh, Lansana; Moigboi, Alex; Momoh, Mambu; Fullah, Mohammed; Moses, Lina M; Brown, Bethany L; Andersen, Kristian G; Winnicki, Sarah; Schaffner, Stephen F; Park, Daniel J; Yozwiak, Nathan L; Jiang, Pan-Pan; Kargbo, David; Jalloh, Simbirie; Fonnie, Mbalu; Sinnah, Vandi; French, Issa; Kovoma, Alice; Kamara, Fatima K; Tucker, Veronica; Konuwa, Edwin; Sellu, Josephine; Mustapha, Ibrahim; Foday, Momoh; Yillah, Mohamed; Kanneh, Franklyn; Saffa, Sidiki; Massally, James L B; Boisen, Matt L; Branco, Luis M; Vandi, Mohamed A; Grant, Donald S; Happi, Christian; Gevao, Sahr M; Fletcher, Thomas E; Fowler, Robert A; Bausch, Daniel G; Sabeti, Pardis C; Khan, S Humarr; Garry, Robert F

2014-11-27

Limited clinical and laboratory data are available on patients with Ebola virus disease (EVD). The Kenema Government Hospital in Sierra Leone, which had an existing infrastructure for research regarding viral hemorrhagic fever, has received and cared for patients with EVD since the beginning of the outbreak in Sierra Leone in May 2014. We reviewed available epidemiologic, clinical, and laboratory records of patients in whom EVD was diagnosed between May 25 and June 18, 2014. We used quantitative reverse-transcriptase-polymerase-chain-reaction assays to assess the load of Ebola virus (EBOV, Zaire species) in a subgroup of patients. Of 106 patients in whom EVD was diagnosed, 87 had a known outcome, and 44 had detailed clinical information available. The incubation period was estimated to be 6 to 12 days, and the case fatality rate was 74%. Common findings at presentation included fever (in 89% of the patients), headache (in 80%), weakness (in 66%), dizziness (in 60%), diarrhea (in 51%), abdominal pain (in 40%), and vomiting (in 34%). Clinical and laboratory factors at presentation that were associated with a fatal outcome included fever, weakness, dizziness, diarrhea, and elevated levels of blood urea nitrogen, aspartate aminotransferase, and creatinine. Exploratory analyses indicated that patients under the age of 21 years had a lower case fatality rate than those over the age of 45 years (57% vs. 94%, P=0.03), and patients presenting with fewer than 100,000 EBOV copies per milliliter had a lower case fatality rate than those with 10 million EBOV copies per milliliter or more (33% vs. 94%, P=0.003). Bleeding occurred in only 1 patient. The incubation period and case fatality rate among patients with EVD in Sierra Leone are similar to those observed elsewhere in the 2014 outbreak and in previous outbreaks. Although bleeding was an infrequent finding, diarrhea and other gastrointestinal manifestations were common. (Funded by the National Institutes of Health and

Training for Innovation: Capacity-Building in Agricultural Research in Post-War Sierra Leone

ERIC Educational Resources Information Center

Gboku, Matthew L. S.; Bebeley, Jenneh F.

2016-01-01

This paper examines how the Sierra Leone Agricultural Research Institute (SLARI) used training and development to build capacity for innovation in agricultural research following the country's civil war which ended in 2002. The Institute's training for innovation addressed different agricultural product value chains (APVCs) within the framework of…

Birefringence in anisotropic optical fibres studied by polarised light Brillouin reflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, A S; Burdin, V V; Konstantinov, Yu A

2015-01-31

Modal birefringence (the difference between the effective refractive indices of orthogonal polarisation modes) is one of the key parameters of anisotropic single-mode fibres, characterising their ability to preserve a linearly polarised state of input light. This parameter is commonly measured using short pieces of fibre, but such procedures are destructive and allow the birefringence to be determined only at the ends of long fibres. In this study, polarised light Brillouin reflectometry is used to assess birefringence uniformity throughout the length of an anisotropic fibre. (optical fibres)

Microscopie par rayons X dans la fenêtre de l'eau : faisabilité et intérêt pour la biologie d'un instrument de laboratoire

NASA Astrophysics Data System (ADS)

Adam, J. F.; Moy, J. P.

2005-06-01

La biologie étudie des structures ou des phénomènes sub-cellulaires. Pour cela la microscopie est la technique d'observation privilégiée. La résolution spatiale de la microscopie optique s'avère bien souvent insuffisante pour de telles observations. Les techniques plus résolvantes, comme la microscopie électronique par transmission sont souvent destructrices et d'une complexité peu adaptée aux besoins des biologistes. La microscopie par rayons X dans la fenêtre de l'eau permet l'imagerie rapide de cellules dans leur milieu naturel, nécessite peu de préparation et offre des résolutions de quelques dizaines de nanomètres. De plus, il existe un bon contraste naturel entre les structures carbonées (protéines, lipides) et l'eau. Actuellement cette technique est limitée aux centres de rayonnement synchrotron, ce qui impose une planification et des déplacements incompatibles avec les besoins de la biologie. Un tel microscope fonctionnant avec uns source de laboratoire serait d'une grande utilité. Ce document présente un état de l'art de la microscopie par rayons X dans la fenêtre de l'eau. Un cahier des charges détaillé pour un appareil de laboratoire ayant les performances optiques requises par les biologistes est présenté et confronté aux microscopes X de laboratoire déjà existants. Des solutions concernant la source et les optiques sont également discutées.

The stimulated Brillouin scattering during the interaction of picosecond laser pulses with moderate- scale-length plasmas

NASA Astrophysics Data System (ADS)

Gaeris, Andres Claudio

The Stimulated Brillouin Scattering (SBS) instability is studied in moderately short scale-length plasmas. The backscattered and specularly reflected light resulting from the interaction of a pair of high power picosecond duration laser pulses with solid Silicon, Gold and Parylene-N (CH) strip targets was spectrally resolved. The first, weaker laser pulse forms a short scale-length plasma while the second delayed one interacts with the isothermally expanded, underdense region of the plasma. The pulses are generated by the Table Top Terawatt (TTT) laser operating at 1054 nm (infrared) with intensities up to 5.10 16 W/cm2. Single laser pulses only show Lambertian scattering on the target critical surface. Pairs of pulses with high intensity in the second pulse show an additional backscattered, highly blueshifted feature, associated with SBS. Increasing this second pulse intensity even more leads to the appearance of a third feature, even more blueshifted than the second, resulting from the Brillouin sidescattering of the laser pulse reflected on the critical surface. The SBS threshold intensities and enhanced reflectivities for P-polarized light are determined for different plasma density scale-lengths. These measurements agree with the convective thresholds predicted by the SBS theory of Liu, Rosenbluth, and White using plasma profiles simulated by the LILAC code. The spectral position of the Brillouin back- and sidescattered features are determined. The SBS and Doppler shifts are much too small to explain the observed blueshifts. The refractive index shift is of the right magnitude, although more detailed verification is required in the future.

Structural relaxation processes in polyethylene glycol/CCl4 solutions by Brillouin scattering.

PubMed

Pochylski, M; Aliotta, F; Błaszczak, Z; Gapiński, J

2005-03-10

We present results of a Brillouin scattering experiment on solutions of poly(ethylene glycol) of mean molecular mass 600 g/mol (PEG600) in CCl4. The relaxation process detected has been assigned to conformational rearrangements of the polymeric chains, triggered by reorientation of the side groups. The concentration dependencies of the hypersound velocity and normalized absorption are compared against the indications from several models proposed in the literature. The concentration evolution of the system is described in terms of two distinct regimes. At high polymer content, the system is dominated by the structure of the dense polymer, where polymer-polymer interactions, together with excluded volume effects, induce the existence of a preferred local arrangement resulting in a narrow distribution of the relaxation times, with the average value of the relaxation time following a simple Arrhenius temperature dependence. As the concentration decreases, the original structure of the hydrogen bonded polymer network is destroyed, and a number of different local configuration coexist, giving rise to a wider distribution of relaxation times or to a multiple relaxation. At low concentrations, the experimental data are well fitted assuming a Vogel-Fulker-Tammon behavior for the average relaxation time. In addition, the observed deviation from the ideal behavior for the refractive index and the density suggests that CCl4 does not behave as an inert solvent, and due to polarization effects, it can develop local hetero-associated structures via electrostatic interaction with the O-H end groups of the polymeric chains. The hypothesis has been successfully tested by fitting the concentration behavior of the hypersonic velocity to a recent three-component model, suitable to describe the concentration dependence of sound velocity in moderately interacting fluids. The indication of the model furnishes a very high value for the association constant of the PEG600, confirming the

The design of an electron gun switchable between immersed and Brillouin flowa)

NASA Astrophysics Data System (ADS)

Becker, R.; Kester, O.

2012-02-01

An electron gun, which can be switched from immersed flow to Brillouin flow during operation, may have advantages for charge breeders as well as for electron beam ion sources and traps (EBISTs). For EBISTs this allows to change the current density according to the repetition frequency and charge state, for charge breeders and EBISTs a lower current density in immersed flow provides higher acceptance for injected ions, while the higher current density in Brillouin flow results in shorter breeding times and a lower emittance for the extracted beam. Therefore, we have designed such a gun for an EBIS with 5 T central magnetic field and without the use of iron and moving the gun. The gun was placed in the axial fringing field of the 5 T solenoid in such a position that a gate valve can be placed between the gun and the cryostat to allow for simple maintenance. The field at the cathode surface turned out to be only 0.05 T, which is not enough to focus 50 A/cm2 at a few kV. However, if a small normal conducting solenoid is placed over the vacuum tube in position of the gun, a field of 0.1 T may be obtained. With this the use of LaB6 as cathode material results in a magnetic compression of 44 and therewith in a focused current density in the trap region of more than 2000 A/cm2. By reversing the current in the gun solenoid the cathode field can easily compensated to zero. By proper design of the electrodes and the compression region, the gun will be able to deliver a beam in Brillouin flow. While this is interesting by itself - remember the "super-compression" reported on CRYEBIS-I - any magnetic field between zero and the value for immersed flow will result in an electron beam with a wide range of adjustable high current densities. The design tools used have been INTMAG(C) for the calculation of magnetic fields, EGN2(C) for the simulation of the gun and ANALYSE(C) for detailed analysis of the results (for more information see www.egun-igun.com).

The design of an electron gun switchable between immersed and Brillouin flow.

PubMed

Becker, R; Kester, O

2012-02-01

An electron gun, which can be switched from immersed flow to Brillouin flow during operation, may have advantages for charge breeders as well as for electron beam ion sources and traps (EBISTs). For EBISTs this allows to change the current density according to the repetition frequency and charge state, for charge breeders and EBISTs a lower current density in immersed flow provides higher acceptance for injected ions, while the higher current density in Brillouin flow results in shorter breeding times and a lower emittance for the extracted beam. Therefore, we have designed such a gun for an EBIS with 5 T central magnetic field and without the use of iron and moving the gun. The gun was placed in the axial fringing field of the 5 T solenoid in such a position that a gate valve can be placed between the gun and the cryostat to allow for simple maintenance. The field at the cathode surface turned out to be only 0.05 T, which is not enough to focus 50 A∕cm(2) at a few kV. However, if a small normal conducting solenoid is placed over the vacuum tube in position of the gun, a field of 0.1 T may be obtained. With this the use of LaB(6) as cathode material results in a magnetic compression of 44 and therewith in a focused current density in the trap region of more than 2000 A∕cm(2). By reversing the current in the gun solenoid the cathode field can easily compensated to zero. By proper design of the electrodes and the compression region, the gun will be able to deliver a beam in Brillouin flow. While this is interesting by itself--remember the "super-compression" reported on CRYEBIS-I--any magnetic field between zero and the value for immersed flow will result in an electron beam with a wide range of adjustable high current densities. The design tools used have been INTMAG(C) for the calculation of magnetic fields, EGN2(C) for the simulation of the gun and ANALYSE(C) for detailed analysis of the results (for more information see www.egun-igun.com).

The Children's War: Towards Peace in Sierra Leone. A Field Report Assessing the Protection and Assistance Needs of Sierra Leonean Children and Adolescents.

ERIC Educational Resources Information Center

Sommers, Marc

Based on a 3-week field visit to Sierra Leone and Guinea, this report investigates why children (ages 0-17) have become key figures in Sierra Leone's civil war, and explores the problems that war has caused them. The report describes significant new effects of violence on three groups of Sierra Leonean children, very few of whom have received any…

Comparison of social resistance to Ebola response in Sierra Leone and Guinea suggests explanations lie in political configurations not culture

PubMed Central

Wilkinson, Annie; Fairhead, James

2017-01-01

Abstract Sierra Leone and Guinea share broadly similar cultural worlds, straddling the societies of the Upper Guinea Coast with Islamic West Africa. There was, however, a notable difference in their reactions to the Ebola epidemic. As the epidemic spread in Guinea, acts of violent or everyday resistance to outbreak control measures repeatedly followed, undermining public health attempts to contain the crisis. In Sierra Leone, defiant resistance was rarer. Instead of looking to ‘culture’ to explain patterns of social resistance (as was common in the media and in the discourse of responding public health authorities) a comparison between Sierra Leone and Guinea suggests that explanations lie in divergent political practice and lived experiences of the state. In particular the structures of state authority through which the national epidemic response were organised integrated very differently with trusted institutions in each country. Predicting and addressing social responses to epidemic control measures should assess such political-trust configurations when planning interventions. PMID:28366999

Off-axis phonon and photon propagation in porous silicon superlattices studied by Brillouin spectroscopy and optical reflectance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, L. C., E-mail: lcparsons@mun.ca; Andrews, G. T., E-mail: tandrews@mun.ca

2014-07-21

Brillouin light scattering experiments and optical reflectance measurements were performed on a pair of porous silicon-based optical Bragg mirrors which had constituent layer porosity ratios close to unity. For off-axis propagation, the phononic and photonic band structures of the samples were modeled as a series of intersecting linear dispersion curves. Zone-folding was observed for the longitudinal bulk acoustic phonon and the frequency of the probed zone-folded longitudinal phonon was shown to be dependent on the propagation direction as well as the folding order of the mode branch. There was no conclusive evidence of coupling between the transverse and the foldedmore » longitudinal modes. Two additional observed Brillouin peaks were attributed to the Rayleigh surface mode and a possible pseudo-surface mode. Both of these modes were dispersive, with the velocity increasing as the wavevector decreased.« less

A previously undiscovered group of chimpanzees (Pan troglodytes verus) is observed living in the Tonkolili district of Sierra Leone.

PubMed

Halloran, Andrew R; Cloutier, Christina T; Sesay, Papanie Bai

2013-06-01

A previously undocumented group of wild chimpanzees (Pan troglodytes verus) was recently discovered along the Pampana River in the Tonkolili District of Sierra Leone. Based on interviews from local residents (N = 6), we estimate the group size to be approximately 30 individuals. Though this population does not show up in the most recent census of chimpanzees in Sierra Leone, it concurs with findings that indicate most of the chimpanzees in Sierra Leone live scattered throughout the country alongside villages, rather than in protected areas. During a three-week observation in the area, two chimpanzees were hunted and killed. The reason for these deaths, along with other reported instances of hunting in the area, are primarily due to crop-raiding and competition for resources between chimpanzees and humans. We conclude that this is a heavily imperiled population. Based on the ecology of the area and composition of local villages, we propose a number of conservation strategies that will promote a symbiotic relationship between the chimpanzees and human populations residing in the area. © 2013 Wiley Periodicals, Inc.

An electro-optic modulator-assisted wavevector-resolving Brillouin light scattering setup.

PubMed

Neumann, T; Schneider, T; Serga, A A; Hillebrands, B

2009-05-01

Brillouin light scattering spectroscopy is a powerful technique which incorporates several extensions such as space-, time-, phase-, and wavevector-resolution. Here, we report on the improvement of the wavevector-resolving setup by including an electro-optic modulator. This provides a reference to calibrate the position of the diaphragm hole which is used for wavevector selection. The accuracy of this calibration is only limited by the accuracy of the wavevector measurement itself. To demonstrate the validity of the approach the wavevectors of dipole-dominated spin waves excited by a microstrip antenna were measured.

AAS Publishing News: An Interview with Leon Golub

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-06-01

In the lead-up to next weeks 2016 Solar Physics Division (SPD) meeting, we wanted to introduce you to Leon Golub, our new Lead Editor for the Sun and the Heliosphere corridor.Leon is a Senior Astrophysicist in the High Energy Division at the Harvard-Smithsonian Center for Astrophysics. He specializes in studies of solar and stellar magnetic activity, and he has built numerous rocket and satellite instruments to study the Sun and its dynamic behavior.* * * * *Tell me about your field of research and some of your current projects.Ive been working primarily on understanding the dynamics of the solar corona, especially using new types of instrumentation that can provide challenges to our theoretical understanding.Image of the Apollo Telescope Mount on Skylab. [NASA]Why did you choose this field?Shortly after graduating from MIT in experimental high energy physics I found a position with a group that was preparing to launch an X-ray telescope on Skylab as part of the cluster of solar instruments called the Apollo Telescope Mount. I have stayed with that field and related ones ever since.What do you consider to be some of the biggest open questions in solar and heliospheric research today?There are so many major questions that its difficult to just settle on a few. The heliosphere is defined by the extent of the influence of the Sun on the interstellar medium. It is an exciting time in that area of study, because we now have the ability to make impressive new observations that allow us to test our understanding of that outer boundary.Within those limits, the Sun has a major influence on solar system objects via its gravitational pull, its light and heat, and the magnetized plasma and high energy particles that it emits in all directions. We are making major discoveries related to how the Sun has influenced the formation and evolution of the planets, including our own planet.The source of all this influence is, of course, the Sun itself, and we are working to understand

Direct optical transitions at K- and H-point of Brillouin zone in bulk MoS2, MoSe2, WS2, and WSe2

NASA Astrophysics Data System (ADS)

Kopaczek, J.; Polak, M. P.; Scharoch, P.; Wu, K.; Chen, B.; Tongay, S.; Kudrawiec, R.

2016-06-01

Modulated reflectance (contactless electroreflectance (CER), photoreflectance (PR), and piezoreflectance (PzR)) has been applied to study direct optical transitions in bulk MoS2, MoSe2, WS2, and WSe2. In order to interpret optical transitions observed in CER, PR, and PzR spectra, the electronic band structure for the four crystals has been calculated from the first principles within the density functional theory for various points of Brillouin zone including K and H points. It is clearly shown that the electronic band structure at H point of Brillouin zone is very symmetric and similar to the electronic band structure at K point, and therefore, direct optical transitions at H point should be expected in modulated reflectance spectra besides the direct optical transitions at the K point of Brillouin zone. This prediction is confirmed by experimental studies of the electronic band structure of MoS2, MoSe2, WS2, and WSe2 crystals by CER, PR, and PzR spectroscopy, i.e., techniques which are very sensitive to critical points of Brillouin zone. For the four crystals besides the A transition at K point, an AH transition at H point has been observed in CER, PR, and PzR spectra a few tens of meV above the A transition. The spectral difference between A and AH transition has been found to be in a very good agreement with theoretical predictions. The second transition at the H point of Brillouin zone (BH transition) overlaps spectrally with the B transition at K point because of small energy differences in the valence (conduction) band positions at H and K points. Therefore, an extra resonance which could be related to the BH transition is not resolved in modulated reflectance spectra at room temperature for the four crystals.

Transmission network of the 2014-2015 Ebola epidemic in Sierra Leone.

PubMed

Yang, Wan; Zhang, Wenyi; Kargbo, David; Yang, Ruifu; Chen, Yong; Chen, Zeliang; Kamara, Abdul; Kargbo, Brima; Kandula, Sasikiran; Karspeck, Alicia; Liu, Chao; Shaman, Jeffrey

2015-11-06

Understanding the growth and spatial expansion of (re)emerging infectious disease outbreaks, such as Ebola and avian influenza, is critical for the effective planning of control measures; however, such efforts are often compromised by data insufficiencies and observational errors. Here, we develop a spatial-temporal inference methodology using a modified network model in conjunction with the ensemble adjustment Kalman filter, a Bayesian inference method equipped to handle observational errors. The combined method is capable of revealing the spatial-temporal progression of infectious disease, while requiring only limited, readily compiled data. We use this method to reconstruct the transmission network of the 2014-2015 Ebola epidemic in Sierra Leone and identify source and sink regions. Our inference suggests that, in Sierra Leone, transmission within the network introduced Ebola to neighbouring districts and initiated self-sustaining local epidemics; two of the more populous and connected districts, Kenema and Port Loko, facilitated two independent transmission pathways. Epidemic intensity differed by district, was highly correlated with population size (r = 0.76, p = 0.0015) and a critical window of opportunity for containing local Ebola epidemics at the source (ca one month) existed. This novel methodology can be used to help identify and contain the spatial expansion of future (re)emerging infectious disease outbreaks. © 2015 The Author(s).

Reduction of the Nonlinear Phase Shift Induced by Stimulated Brillouin Scattering for Bi-Directional Pumping Configuration System Using Particle Swarm Optimization Algorithm

NASA Astrophysics Data System (ADS)

Al-Asadi, H. A.

2013-02-01

We present a theoretical analysis of an additional nonlinear phase shift of backward Stokes wave based on stimulated Brillouin scattering in the system with a bi-directional pumping scheme. We optimize three parameters of the system: the numerical aperture, the optical loss and the pumping wavelength to minimize an additional nonlinear phase shift of backward Stokes waves due to stimulated Brillouin scattering. The optimization is performed with various Brillouin pump powers and the optical reflectivity values are based on the modern, global evolutionary computation algorithm, particle swarm optimization. It is shown that the additional nonlinear phase shift of backward Stokes wave varies with different optical fiber lengths, and can be minimized to less than 0.07 rad according to the particle swarm optimization algorithm for 5 km. The bi-directional pumping configuration system is shown to be efficient when it is possible to transmit the power output to advanced when frequency detuning is negative and delayed when it is positive, with the optimum values of the three parameters to achieve the reduction of an additional nonlinear phase shift.

Utilization of respondent-driven sampling among a population of child workers in the diamond-mining sector of Sierra Leone.

PubMed

Bjørkhaug, I; Hatløy, A

2009-01-01

This article describes the implementation of respondent driven sampling (RDS) in a study conducted in Kono District, Sierra Leone. RDS was used to identify children, under the age of 18 years old, working in the diamond sector of Sierra Leone. This includes children working directly as diamond miners as well as children working in the informal sector connected to the diamond field. The article seeks to postulate that RDS is a suitable method for a rapid approach to a population that is unidentified in size and demonstrate how RDS can reach a study population within a limited period.

Control of Ebola hemorrhagic fever: vaccine development and our Ebola project in Sierra Leone.

PubMed

Watanabe, Tokiko; Kawaoka, Yoshihiro

2016-01-01

Since December 2013, West Africa has experienced the worst Ebola virus outbreak in recorded history. Of the 28,639 cases reported to the World Health Organization as of March 2016, nearly half (14,124) occurred in Sierra Leone. With a case fatality rate of approximately 40%, this outbreak has claimed the lives of 11,316 individuals. No FDA-approved vaccines or drugs are available to prevent or treat Ebola virus infection. Experimental vaccines and therapies are being developed; however, their safety and efficacy are still being evaluated. Therefore, there is an urgent need to develop control measures to prevent or limit future Ebola virus outbreaks.Previously, we developed a replication-defective Ebola virus that lacks the coding region for the essential viral transcription activator VP30 (Ebola ΔVP30 virus). Here, we evaluated the vaccine efficacy of Ebola ΔVP30 virus in a non-human primate model and describe our collaborative Ebola project in Sierra Leone.

The Violence of Peace and the Role of Education: Insights from Sierra Leone

ERIC Educational Resources Information Center

Novelli, Mario; Higgins, Sean

2017-01-01

Research on peacebuilding has mushroomed over the last decade and there is a growing interest in the role of education in supporting peacebuilding processes. This paper engages with these debates, UN peacebuilding activities and the location of education initiatives therein, through a case study of Sierra Leone. In the first part, we explore the…

Brillouin light scattering studies of the mechanical properties of ultrathin low-k dielectric films

NASA Astrophysics Data System (ADS)

Link, A.; Sooryakumar, R.; Bandhu, R. S.; Antonelli, G. A.

2006-07-01

In an effort to reduce RC time delays that accompany decreasing feature sizes, low-k dielectric films are rapidly emerging as potential replacements for silicon dioxide (SiO2) at the interconnect level in integrated circuits. The main challenge in low-k materials is their substantially weaker mechanical properties that accompany the increasing pore volume content needed to reduce k. We show that Brillouin light scattering is an excellent nondestructive technique to monitor and characterize the mechanical properties of these porous films at thicknesses well below 200nm that are pertinent to present applications. Observation of longitudinal and transverse standing wave acoustic resonances and the dispersion that accompany their transformation into traveling waves with finite in-plane wave vectors provides for a direct measure of the principal elastic constants that completely characterize the mechanical properties of these ultrathin films. The mode amplitudes of the standing waves, their variation within the film, and the calculated Brillouin intensities account for most aspects of the spectra. We further show that the values obtained by this method agree well with other experimental techniques such as nanoindentation and picosecond laser ultrasonics.

From Sommerfeld and Brillouin forerunners to optical precursors

NASA Astrophysics Data System (ADS)

Macke, Bruno; Ségard, Bernard

2013-04-01

The Sommerfeld and Brillouin forerunners generated in a single-resonance absorbing medium by an incident step-modulated pulse are theoretically considered in the double limit where the susceptibility of the medium is weak and the resonance is narrow. Combining direct Laplace-Fourier integration and calculations by the saddle-point method, we establish an explicit analytical expression of the transmitted field valid at any time, even when the two forerunners significantly overlap. We examine how their complete overlapping, occurring for shorter propagation distances, originates the formation of the unique transient currently named resonant precursor or dynamical beat. We obtain an expression of this transient identical to that usually derived within the slowly varying envelope approximation in spite of the initial discontinuity of the incident field envelope. The dynamical beats and 0π pulses generated by ultrashort incident pulses are also briefly examined.

The Great War and Remembrance in Jose Leon Machado's "Memoria das Estrelas sem Brilho"

ERIC Educational Resources Information Center

Azevedo, Milton M.

2011-01-01

This article analyzes Jose Leon Machado's novel, "Memoria das Estrelas sem Brilho," as a multilayered historical novel in which a war story provides a background for comments on aspects of early twentieth-century Portuguese society, such as male bonding, religion, sexual mores, and social stratification. (Contains 11 notes.)

Guided Acoustic and Optical Waves in Silicon-on-Insulator for Brillouin Scattering and Optomechanics

DTIC Science & Technology

2016-08-01

APL PHOTONICS 1, 071301 (2016) Guided acoustic and optical waves in silicon-on- insulator for Brillouin scattering and optomechanics Christopher J...is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin...mechanism on which to base on-chip nonlinear optical devices compatible with a rapidly growing silicon photonics toolbox.3–9 While silicon on insulator

Empowering Women through Education: Evidence from Sierra Leone. NBER Working Paper No. 18016

ERIC Educational Resources Information Center

Mocan, Naci H.; Cannonier, Colin

2012-01-01

We use data from Sierra Leone where a substantial education program provided increased access to education for primary-school age children but did not benefit children who were older. We exploit the variation in access to the program generated by date of birth and the variation in resources between various districts of the country. We find that…

Untreated head and neck surgical disease in Sierra Leone: a cross-sectional, countrywide survey.

PubMed

Van Buren, Nicholas C; Groen, Reinou S; Kushner, Adam L; Samai, Mohamed; Kamara, Thaim B; Ying, Jian; Meier, Jeremy D

2014-10-01

Demonstrate how the Surgeons OverSeas Assessment of Surgical Need (SOSAS) can be used to determine the burden of head and neck (H&N) surgical disease in developing countries and identify reasons for untreated disease. Cluster randomized, cross-sectional, countrywide survey. Sierra Leone. The survey was administered to 75 of 9671 enumeration areas in Sierra Leone between January 9 and February 3, 2012, with 25 households in each cluster randomly selected for the survey. A household representative and 2 randomly selected household members were interviewed. Need for surgical care was based on participants' responses to whether they had an H&N condition that they believed needed surgical care. Of 1875 households, data were analyzed for 1843 (98%), with 3645 total respondents. Seven hundred and one H&N surgical conditions were reported as occurring during the lifetime of the 3645 respondents (19.2%).The current prevalence of H&N conditions in need of a surgical consultation was 11.8%. No money (60.1%) was the most common reason respondents reported for not receiving medical care. A bivariate analysis demonstrated that age, village type, education, and type of condition may be predictors for seeking health care and/or receiving surgical care. These results show limited access for patients to be evaluated for a potential H&N surgical condition in Sierra Leone. The true incidence of untreated surgical disease is unknown as most respondents were not evaluated by a surgeon. This survey could be used in other countries as health care professionals assess surgical needs throughout the world. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

Developmental Differences in Motor Task Integration: A Test of Pascual-Leone's Theory of Constructive Operators.

ERIC Educational Resources Information Center

Todor, John I.

1979-01-01

Assesses the ability of Pascual-Leone's Theory of Constructive Operators to predict the minimum age or maturational level at which integration of a motor task could be achieved. Subjects were 114 elementary school children ranging in age from 5 to 12. (Author/MP)

Prevalence and Risk Factors for Human Immunodeficiency Virus (HIV) and Syphilis Infections Among Military Personnel in Sierra Leone.

PubMed

Djibo, Djeneba Audrey; Sahr, Foday; McCutchan, J Allen; Jain, Sonia; Araneta, Maria Rosario G; Brodine, Stephanie K; Shaffer, Richard A

2017-01-01

HIV and syphilis infections are common in military personnel in sub-Saharan Africa, which impact combat preparedness and increase demands on the military health care system. The prevalence of HIV is estimated at 1.5% among the general population (15-49 years of age) of Sierra Leone, and the estimated syphilis prevalence ranged from 1.5% to 5.2% based on regional studies. We examined the prevalence and risk factors for these two common sexually transmitted infections in the Sierra Leone military personnel. This cross-sectional study examined 1157 randomly selected soldiers from the Republic of Sierra Leone Armed Forces in 2013 using computer-assisted personal interviews and rapid testing algorithms. Descriptive statistics and logistic regression models were implemented to identify risk factors for HIV and syphilis separately. The mean age of participants was 38 years, 11.1% were female, and 86.5% were married. The seroprevalence of HIV and syphilis were 3.3% (95% confidence interval [CI]: 2.3%-4.3%) and 7.3% (95% CI: 5.9%-8.8%), respectively. Lower educational attainment in women, multiple sexual partners, unintended sex after alcohol use and use of condoms were independently associated with HIV status (p<0.05). After adjustment, HIV infection was associated with female gender, unintended sex after alcohol use, condom use at last sex, having multiple sexual partnerships in the same week and HIV testing outside of military facilities (p<0.05). Increasing age, positive HIV status and rural regions of residence were associated with syphilis seropositivity. The prevalence of sexually transmitted infections among military personnel was higher than the general population of Sierra Leone. Several high-risk sexual behaviors that expose soldiers to HIV and syphilis could be addressed through prevention interventions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Pilot study on rugged fiber optic brillouin sensors for large-strain measurements to ensure the safety of transportation structures.

DOT National Transportation Integrated Search

2012-07-01

Brillouin-scattering Optical Time Domain Reflectometry (BOTDR) is a viable technology for simultaneous, distributed : strain and temperature measurements for miles-long transportation structures. It is a promising tool to ensure the smooth : operatio...

Rapid assessment of Ebola infection prevention and control needs--six districts, Sierra Leone, October 2014.

PubMed

Pathmanathan, Ishani; O'Connor, Katherine A; Adams, Monica L; Rao, Carol Y; Kilmarx, Peter H; Park, Benjamin J; Mermin, Jonathan; Kargbo, Brima; Wurie, Alie H; Clarke, Kevin R

2014-12-12

As of October 31, 2014, the Sierra Leone Ministry of Health and Sanitation had reported 3,854 laboratory-confirmed cases of Ebola virus disease (Ebola) since the outbreak began in May 2014; 199 (5.2%) of these cases were among health care workers. Ebola infection prevention and control (IPC) measures are essential to interrupt Ebola virus transmission and protect the health workforce, a population that is disproportionately affected by Ebola because of its increased risk of exposure yet is essential to patient care required for outbreak control and maintenance of the country's health system at large. To rapidly identify existing IPC resources and high priority outbreak response needs, an assessment by CDC Ebola Response Team members was conducted in six of the 14 districts in Sierra Leone, consisting of health facility observations and structured interviews with key informants in facilities and government district health management offices. Health system gaps were identified in all six districts, including shortages or absence of trained health care staff, personal protective equipment (PPE), safe patient transport, and standardized IPC protocols. Based on rapid assessment findings and key stakeholder input, priority IPC actions were recommended. Progress has since been made in developing standard operating procedures, increasing laboratory and Ebola treatment capacity and training the health workforce. However, further system strengthening is needed. In particular, a successful Ebola outbreak response in Sierra Leone will require an increase in coordinated and comprehensive district-level IPC support to prevent ongoing Ebola virus transmission in household, patient transport, and health facility settings.

Two-dimensional simulations of stimulated Brillouin scattering in laser produced plasmas

NASA Astrophysics Data System (ADS)

Amin, M. R.; Capjack, C. E.; Frycz, P.; Rozmus, W.; Tikhonchuk, V. T.

1993-07-01

A system of electromagnetic and ion acoustic wave equations coupled via the ponderomotive force are solved numerically in a two-dimensional planar geometry. The competition between forward, side, and backward Brillouin scattering of the finite size laser beam is studied for the first time without the standard paraxial optics approximation. Simulations reveal a strong dependence of the scattered light characteristics on the geometry of the interaction region, the shape of the pump beam, and the ion acoustic wave damping. The main effects include side and forward scattering enhancement and a stimulation of collimated backward scattered radiation.

All-optical flip-flops based on dynamic Brillouin gratings in fibers.

PubMed

Soto, Marcelo A; Denisov, Andrey; Angulo-Vinuesa, Xabier; Martin-Lopez, Sonia; Thévenaz, Luc; Gonzalez-Herraez, Miguel

2017-07-01

A method to generate an all-optical flip-flop is proposed and experimentally demonstrated based on dynamic Brillouin gratings (DBGs) in polarization maintaining fibers. In a fiber with sufficiently uniform birefringence, this flip-flop can provide extremely long storage times and ultra-wide bandwidth. The experimental results demonstrate an all-optical flip-flop operation using phase-modulated pulses of 300 ps and a 1 m long DBG. This has led to a time-bandwidth product of ∼30, being in this proof-of-concept setup mainly limited by the relatively low bandwidth of the used pulses and the short fiber length.

When free healthcare is not free. Corruption and mistrust in Sierra Leone's primary healthcare system immediately prior to the Ebola outbreak.

PubMed

Pieterse, Pieternella; Lodge, Tom

2015-11-01

Sierra Leone is one of three countries recently affected by Ebola. In debates surrounding the circumstances that contributed to the initial failure to contain the outbreak, the word 'trust' is often used: In December 2014, WHO director Margret Chan used 'lack of trust in governments'; The Lancet's Editor-in-Chief, wrote how Ebola has exposed the '… breakdown of trust between communities and their governments.' This article explores the lack of trust in public healthcare providers in Sierra Leone, predating the Ebola outbreak, apparently linked to widespread petty corruption in primary healthcare facilities. It compares four NGO-supported accountability interventions targeting Sierra Leone's primary health sector. Field research was conducted in Kailahun, Kono and Tonkolili Districts, based on interviews with health workers and focus group discussions with primary healthcare users. Field research showed that in most clinics, women and children entitled to free care routinely paid for health services. A lack of accountability in Sierra Leone's health sector appears pervasive at all levels. Petty corruption is rife. Understaffing leads to charging for free care in order to pay clinic-based 'volunteers' who function as vaccinators, health workers and birth attendants. Accountability interventions were found to have little impact on healthworker (mis)behaviour. © The Author 2015. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Binational Teacher Development: Teacher Ambassador Exchange Program, New Mexico, USA and Nuevo Leon, Mexico.

ERIC Educational Resources Information Center

Habermann, Mary Jean

The report describes the rationale for and history of an exchange program for Nuevo Leon (Mexico) and New Mexico bilingual education teachers. The program evolved from the need to help Spanish-speaking students maintain their own language and culture while in the United States. New Mexico's state policy concerning language-minority children and…

Remote Water Temperature Measurements Based on Brillouin Scattering with a Frequency Doubled Pulsed Yb:doped Fiber Amplifier

PubMed Central

Schorstein, Kai; Popescu, Alexandru; Göbel, Marco; Walther, Thomas

2008-01-01

Temperature profiles of the ocean are of interest for weather forecasts, climate studies and oceanography in general. Currently, mostly in situ techniques such as fixed buoys or bathythermographs deliver oceanic temperature profiles. A LIDAR method based on Brillouin scattering is an attractive alternative for remote sensing of such water temperature profiles. It makes it possible to deliver cost-effective on-line data covering an extended region of the ocean. The temperature measurement is based on spontaneous Brillouin scattering in water. In this contribution, we present the first water temperature measurements using a Yb:doped pulsed fiber amplifier. The fiber amplifier is a custom designed device which can be operated in a vibrational environment while emitting narrow bandwidth laser pulses. The device shows promising performance and demonstrates the feasibility of this approach. Furthermore, the current status of the receiver is briefly discussed; it is based on an excited state Faraday anomalous dispersion optical filter. PMID:27873842

Time and frequency pump-probe multiplexing to enhance the signal response of Brillouin optical time-domain analyzers.

PubMed

Soto, Marcelo A; Ricchiuti, Amelia Lavinia; Zhang, Liang; Barrera, David; Sales, Salvador; Thévenaz, Luc

2014-11-17

A technique to enhance the response and performance of Brillouin distributed fiber sensors is proposed and experimentally validated. The method consists in creating a multi-frequency pump pulse interacting with a matching multi-frequency continuous-wave probe. To avoid nonlinear cross-interaction between spectral lines, the method requires that the distinct pump pulse components and temporal traces reaching the photo-detector are subject to wavelength-selective delaying. This way the total pump and probe powers launched into the fiber can be incrementally boosted beyond the thresholds imposed by nonlinear effects. As a consequence of the multiplied pump-probe Brillouin interactions occurring along the fiber, the sensor response can be enhanced in exact proportion to the number of spectral components. The method is experimentally validated in a 50 km-long distributed optical fiber sensor augmented to 3 pump-probe spectral pairs, demonstrating a signal-to-noise ratio enhancement of 4.8 dB.

Brillouin light scattering spectroscopy for tissue engineering application

NASA Astrophysics Data System (ADS)

Akilbekova, Dana; Yakupov, Talgat; Ogay, Vyacheslav; Umbayev, Bauyrzhan; Yakovlev, Vladislav V.; Utegulov, Zhandos N.

2018-02-01

Biomechanical properties of mammalian bones, such as strength, toughness and plasticity, are essential for understanding how microscopic scale mechanical features can link to macroscale bones' strength and fracture resistance. We employ Brillouin light scattering (BLS) micro-spectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins (BMPs) and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free imaging modality for probing mechanical properties of hard tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that HCF gels containing combination of all factors had the best effect with complete defect regeneration at week 9 and that the bones with fully consolidated fractures have higher values of elastic moduli compared to the bones with defects.

An Introduction to Isaac Leon Kandel: Who He Was and Why He Matters

ERIC Educational Resources Information Center

Null, J. Wesley

2007-01-01

Few professors of education in the 21st century know the name Isaac Leon Kandel. A Kappa Delta Pi Laureate and author of more than 20 books, Kandel may be known to scholars who specialize in comparative education or educational history; however, Kandel is known to very few beyond these two fields. This article is a testament to Kandel, his…

Assessing biodiversity in Nuevo Leon, Mexico: Are nature reserves the answer?

USGS Publications Warehouse

Cantu, C.; Wright, R.G.; Scott, J.M.; Strand, Espen

2004-01-01

The Mexican state of Nuevo Leon, located in the northeastern portion of the country, currently has 26 state and three federal nature reserves covering approximately 4.5% of its land area. These reserves were established for a variety of reasons not necessarily related to conservation purposes. In 2000 in response to a growing concern about the lack of organized conservation reserve planning to protect the important biological and physical features of Mexico, the Mexican Commission for Knowledge and Use of Biodiversity proposed 12 new terrestrial reserves for Nuevo Leon. The new reserves, if established, would increase the proportion of protected lands in the state to almost 24% of the state's land area. We compiled a Geographic Information System (GIS) analysis using digital thematic maps of physical and ecological features to examine how well the existing and proposed reserves incorporated the major biological and physical features of the state. The existing reserves are located primarily in regions with elevations > 1,000-1,500 m, on less productive soils, and are dominated by pine and oak forest cover types. As a result, the state's dominant biotic region - low elevation coastal plain with xeric scrub vegetation - is disproportionately under represented in the current reserve system. The new reserves would expand the protection of biophysical resources throughout the state. However, the inclusion of important resources in the low elevation coastal lands would still be limited.

Aircraft laser sensing of sound velocity in water - Brillouin scattering

NASA Technical Reports Server (NTRS)

Hickman, G. D.; Harding, John M.; Carnes, Michael; Pressman, AL; Kattawar, George W.; Fry, Edward S.

1991-01-01

A real-time data source for sound speed in the upper 100 m has been proposed for exploratory development. This data source is planned to be generated via a ship- or aircraft-mounted optical pulsed laser using the spontaneous Brillouin scattering technique. The system should be capable (from a single 10 ns 500 mJ pulse) of yielding range resolved sound speed profiles in water to depths of 75-100 m to an accuracy of 1 m/s. The 100 m profiles will provide the capability of rapidly monitoring the upper-ocean vertical structure. They will also provide an extensive, subsurface-data source for existing real-time, operational ocean nowcast/forecast systems.

Brillouin scattering-induced rogue waves in self-pulsing fiber lasers

PubMed Central

Hanzard, Pierre-Henry; Talbi, Mohamed; Mallek, Djouher; Kellou, Abdelhamid; Leblond, Hervé; Sanchez, François; Godin, Thomas; Hideur, Ammar

2017-01-01

We report the experimental observation of extreme instabilities in a self-pulsing fiber laser under the influence of stimulated Brillouin scattering (SBS). Specifically, we observe temporally localized structures with high intensities that can be referred to as rogue events through their statistical behaviour with highly-skewed intensity distributions. The emergence of these SBS-induced rogue waves is attributed to the interplay between laser operation and resonant Stokes orders. As this behaviour is not accounted for by existing models, we also present numerical simulations showing that such instabilities can be observed in chaotic laser operation. This study opens up new possibilities towards harnessing extreme events in highly-dissipative systems through adapted laser cavity configurations. PMID:28374840

Brillouin scattering-induced rogue waves in self-pulsing fiber lasers.

PubMed

Hanzard, Pierre-Henry; Talbi, Mohamed; Mallek, Djouher; Kellou, Abdelhamid; Leblond, Hervé; Sanchez, François; Godin, Thomas; Hideur, Ammar

2017-04-04

We report the experimental observation of extreme instabilities in a self-pulsing fiber laser under the influence of stimulated Brillouin scattering (SBS). Specifically, we observe temporally localized structures with high intensities that can be referred to as rogue events through their statistical behaviour with highly-skewed intensity distributions. The emergence of these SBS-induced rogue waves is attributed to the interplay between laser operation and resonant Stokes orders. As this behaviour is not accounted for by existing models, we also present numerical simulations showing that such instabilities can be observed in chaotic laser operation. This study opens up new possibilities towards harnessing extreme events in highly-dissipative systems through adapted laser cavity configurations.

Distinguishing Raman from strongly coupled Brillouin amplification for short pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Qing; Barth, Ido; Edwards, Matthew R.

2016-05-15

Plasma-based amplification by strongly coupled Brillouin scattering has recently been suggested for the compression of a short seed laser to ultrahigh intensities in sub-quarter-critical-density plasmas. However, by employing detailed spectral analysis of particle-in-cell simulations in the same parameter regime, we demonstrate that, in fact, Raman backscattering amplification is responsible for the growth and compression of the high-intensity, leading spike, where most of the energy compression occurs, while the ion mode only affects the low-intensity tail of the amplified pulse. The critical role of the initial seed shape is identified. A number of subtleties in the numerical simulations are also pointedmore » out.« less

Chern-Simons theory and Wilson loops in the Brillouin zone

NASA Astrophysics Data System (ADS)

Lian, Biao; Vafa, Cumrun; Vafa, Farzan; Zhang, Shou-Cheng

2017-03-01

Berry connection is conventionally defined as a static gauge field in the Brillouin zone. Here we show that for three-dimensional (3D) time-reversal invariant superconductors, a generalized Berry gauge field behaves as a fluctuating field of a Chern-Simons gauge theory. The gapless nodal lines in the momentum space play the role of Wilson loop observables, while their linking and knot invariants modify the gravitational theta angle. This angle induces a topological gravitomagnetoelectric effect where a temperature gradient induces a rotational energy flow. We also show how topological strings may be realized in the six-dimensional phase space, where the physical space defects play the role of topological D-branes.

Youth Reintegration Training and Education for Peace (YRTEP) Program: Sierra Leone, 2000-2001. Impact Evaluation.

ERIC Educational Resources Information Center

Fauth, Gloria; Daniels, Bonnie

Management Systems International (MSI), with funding from United States Agency for International Development Office of Transition Initiatives (USAID/OTI) and in coordination with other partners, is implementing a program in Sierra Leone entitled "Youth Reintegration Training and Education for Peace" (YRTEP). The object is to provide…

Characterization of the dengue outbreak in Nuevo Leon state, Mexico, 2010.

PubMed

Leduc-Galindo, D; Gloria-Herrera, U; Rincón-Herrera, U; Ramos-Jiménez, J; Garcia-Luna, S; Arellanos-Soto, D; Mendoza-Tavera, N; Tavitas-Aguilar, I; Garcia-Garcia, E; Galindo-Galindo, E; Villarreal-Perez, J; Fernandez-Salas, I; Santiago, G A; Muñoz-Jordan, J; Rivas-Estilla, A M

2015-04-01

We studied serotypes circulating dengue virus (DENV) cases, entomological Breteau index, rain-fall index and epidemiology of groups affected during the 2010 outbreak in Nuevo Leon, Mexico. From 2,271 positive cases, 94% were dengue classic and 6% dengue hemorrhagic fever; DENV1 was mainly isolated (99%) (Central-American lineage of American-African-genotype). We found correlation between two environmental phenomena (Increment of rainfall and vector-indexes) (p ≤ 0.05) with epidemiological, clinical and risk of DENV-1 ongoing transmission.

Excitons at the center of the Brillouin zone in CuB{sub 2}O{sub 4} magnetoelectric

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menshenin, V. V., E-mail: menshenin@imp.uran.ru

2017-02-15

The possibility of exciton excitation in CuB{sub 2}O{sub 4} magnetoelectric at point Γ(0, 0, 0) of the Brillouin zone has been analyzed using group theory. All possible orientations of the electric and magnetic fields that permit the excitation of these excitons have been determined.

Identifying spatio-temporal dynamics of Ebola in Sierra Leone using virus genomes

PubMed Central

Proctor, Joshua L.

2017-01-01

Containing the recent West African outbreak of Ebola virus (EBOV) required the deployment of substantial global resources. Despite recent progress in analysing and modelling EBOV epidemiological data, a complete characterization of the spatio-temporal spread of Ebola cases remains a challenge. In this work, we offer a novel perspective on the EBOV epidemic in Sierra Leone that uses individual virus genome sequences to inform population-level, spatial models. Calibrated to phylogenetic linkages of virus genomes, these spatial models provide unique insight into the disease mobility of EBOV in Sierra Leone without the need for human mobility data. Consistent with other investigations, our results show that the spread of EBOV during the beginning and middle portions of the epidemic strongly depended on the size of and distance between populations. Our phylodynamic analysis also revealed a change in model preference towards a spatial model with power-law characteristics in the latter portion of the epidemic, correlated with the timing of major intervention campaigns. More generally, we believe this framework, pairing molecular diagnostics with a dynamic model selection procedure, has the potential to be a powerful forecasting tool along with offering operationally relevant guidance for surveillance and sampling strategies during an epidemic. PMID:29187639

Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser assisted by multiple four-wave mixing processes in a ring cavity

NASA Astrophysics Data System (ADS)

Shirazi, M. R.; Mohamed Taib, J.; De La Rue, R. M.; Harun, S. W.; Ahmad, H.

2015-03-01

Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser (MBRFL) assisted by four-wave mixing have been investigated through the development of Stokes and anti-Stokes lines under different combinations of Brillouin and Raman pump power levels and different Raman pumping schemes in a ring cavity. For a Stokes line of order higher than three, the threshold power was less than the saturation power of its last-order Stokes line. By increasing the Brillouin pump power, the nth order anti-Stokes and the (n+4)th order Stokes power levels were unexpectedly increased almost the same before the Stokes line threshold power. It was also found out that the SBS threshold reduction (SBSTR) depended linearly on the gain factor for the 1st and 2nd Stokes lines, as the first set. This relation for the 3rd and 4th Stokes lines as the second set, however, was almost linear with the same slope before SBSTR -6 dB, then, it approached to the linear relation in the first set when the gain factor was increased to 50 dB. Therefore, the threshold power levels of Stokes lines for a given Raman gain can be readily estimated only by knowing the threshold power levels in which there is no Raman amplification.

Brillouin light scattering studies on the mechanical properties of ultrathin, porous low-K dielectric films

NASA Astrophysics Data System (ADS)

Zhou, Wei; Sooryakumar, R.; King, Sean

2010-03-01

Low K dielectrics have predominantly replaced silicon dioxide as the interlayer dielectric material for interconnects in state of the art integrated circuits. To further reduce interconnect resistance-capacitance (RC) delays, additional reductions in the K for these low-K materials is being pursued by the introduction of controlled levels of porosity. The main challenge for porous low-K dielectrics is the substantial reduction in mechanical properties that is accompanied by the increased pore volume content needed to reduce K. We report on the application of the nondestructive Brillouin light scattering technique to monitor and characterize the mechanical properties of these porous films at thicknesses well below 200 nm that are pertinent to present applications. Observation of longitudinal and transverse standing wave acoustic resonances and the dispersion that accompany their transformation into traveling waves with finite in-plane wave vectors provides for the principal elastic constants that completely characterize the mechanical properties of these porous films. The mode amplitudes of the standing waves, their variation within the film, and the calculated Brillouin intensities account for most aspects of the spectra. The resulting elastic constants are compared with corresponding values obtained from other experimental techniques.

The Auto-Bäcklund transformations for the (2+1)-dimensional Boiti-Leon-Manna-Pempinelli equation

NASA Astrophysics Data System (ADS)

Kaplan, Melike; Akbulut, Arzu; Bekir, Ahmet

2017-01-01

In this work, the homogeneous balance method is used to construct Auto-Bäcklund transformation of the Boiti-Leon-Manna-Pempinelli (BLMP) equation. With the aid of the transformations founded in this paper and Maple packet programme, abundant exact and explicit solutions to the BLMP equation are constructed.

Linking Research, Extension and Farmers: The Case of Mangrove Swamp Rice Cultivation in Sierra Leone.

ERIC Educational Resources Information Center

Zinnah, Moses Moroe

1994-01-01

Interviews with 124 rice farmers in Sierra Leone revealed that farmers and extension staff have minimal participation and input in testing of new cultivation technologies. The top-down research approach has limited contact among researchers, extension staff, and farmers and affected the utility and application of research. (SK)

Stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor

NASA Astrophysics Data System (ADS)

Ferdous, T.; Salahuddin, M.; Amin, M. R.; Salimullah, M.

1995-09-01

In the present paper we have studied the stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor. The nonlinearity in the low-frequency ion-acoustic wave arises through the ponderomotive force on both electrons and holes. The high-frequency nonlinearity arises through the nonlinear current density. For typical plasma parameters in compensated Ge, ɛL=16, T0=77 K, n00=1017 cm-3, Bs=60 kG, θ=30°, laser power density corresponding to a CO2 laser ~=0.1 MW cm-2, the growth rate of the low-frequency ion-acoustic wave turns out to be ~=107 rad sec-1.

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leon reservoirs, Chihuahua, Mexico

NASA Astrophysics Data System (ADS)

Méndez-García, C.; Renteria-Villalobos, M.; García-Tenorio, R.; Montero-Cabrera, M. E.

2014-07-01

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. 232Th-series, 238U-series, 40K and 137Cs activity concentrations (AC, Bq kg-1) were determined by gamma spectrometry with a high purity Ge detector. 238U and 234U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating of core sediments was performed applying CRS method to 210Pb activities. Results were verified by 137Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High 238U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento - Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) 234U/overflow="scroll">238U and 238U/overflow="scroll">226Ra in sediments have values between 0.9-1.2, showing a behavior close to radioactive equilibrium in the entire basin. 232Th/overflow="scroll">238U, 228Ra/overflow="scroll">226Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs.

High and equitable mass vitamin A supplementation coverage in Sierra Leone: a post-event coverage survey.

PubMed

Hodges, Mary H; Sesay, Fatmata F; Kamara, Habib I; Turay, Mohamed; Koroma, Aminata S; Blankenship, Jessica L; Katcher, Heather I

2013-08-01

In Sierra Leone, children ages 6-59 months receive twice-yearly vitamin A supplementation (VAS) through Maternal and Child Health Week (MCHW) events. VAS coverage in 2011 was calculated using government tally sheets of vitamin A capsule distribution and outdated population projections from the 2004 census. We conducted a national post-event coverage (PEC) survey to validate coverage and inform strategies to reach universal coverage of VAS in Sierra Leone. Immediately following the November 2011 MCHW event, we conducted a national PEC survey by interviewing caregivers with children ages 6-59 months using a randomized 30X30 cluster design (N = 900). We also interviewed one health worker and one community health worker in each cluster to determine their knowledge about VAS (N = 60). VAS coverage was 91.8% among children ages 6-59 months, which was lower than the 105.1% reported through tally sheets. Coverage was high and equitable among all districts and between age groups (98.5% for infants ages 6-11 months and 90.5% for children ages 12-59 months). Major reasons for not receiving VAS were that the child was out of the area (42.4%), the household was not visited by community health workers (28.0%), and the caretaker was not aware of the event (11.9%). Twice-yearly delivery of VAS through MCHW events achieved consistently high and equitable coverage in Sierra Leone. Universal coverage may be achieved through continued focus on communication and targeted outreach to hard-to-reach areas during the MCHWs.

Biomechanics of subcellular structures by non-invasive Brillouin microscopy

NASA Astrophysics Data System (ADS)

Antonacci, Giuseppe; Braakman, Sietse

2016-11-01

Cellular biomechanics play a pivotal role in the pathophysiology of several diseases. Unfortunately, current methods to measure biomechanical properties are invasive and mostly limited to the surface of a cell. As a result, the mechanical behaviour of subcellular structures and organelles remains poorly characterised. Here, we show three-dimensional biomechanical images of single cells obtained with non-invasive, non-destructive Brillouin microscopy with an unprecedented spatial resolution. Our results quantify the longitudinal elastic modulus of subcellular structures. In particular, we found the nucleoli to be stiffer than both the nuclear envelope (p < 0.0001) and the surrounding cytoplasm (p < 0.0001). Moreover, we demonstrate the mechanical response of cells to Latrunculin-A, a drug that reduces cell stiffness by preventing cytoskeletal assembly. Our technique can therefore generate valuable insights into cellular biomechanics and its role in pathophysiology.

Reconstruction versus Transformation: Post-War Education and the Struggle for Gender Equity in Sierra Leone

ERIC Educational Resources Information Center

Maclure, Richard; Denov, Myriam

2009-01-01

In post-war contexts, education is widely regarded as essential not only for civic reconciliation, but also as a key force for gender equity. In Sierra Leone, however, despite enhanced educational opportunities for girls, much of the emphasis on post-war educational reconstruction is unlikely to rectify gender inequities that remain entrenched…

A systematic study of Rayleigh-Brillouin scattering in air, N₂, and O₂ gases.

PubMed

Gu, Ziyu; Ubachs, Wim

2014-09-14

Spontaneous Rayleigh-Brillouin scattering experiments in air, N2, and O2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90° scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N2 and O2. Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in the 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy for N2 and O2, as well as for air. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm, and for the pressure-temperature parameter space covered in the present study (250-340 K and 0.6-3 bars). In the application of the Tenti S6 model, based on the transport coefficients of the gases, such as thermal conductivity κ, internal specific heat capacity c(int) and shear viscosity η, as well as their temperature dependencies taken as inputs, values for the more elusive bulk viscosity η(b) for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of

Lie symmetry analysis, Bäcklund transformations, and exact solutions of a (2 + 1)-dimensional Boiti-Leon-Pempinelli system

NASA Astrophysics Data System (ADS)

Zhao, Zhonglong; Han, Bo

2017-10-01

In this paper, the Lie symmetry analysis method is employed to investigate the Lie point symmetries and the one-parameter transformation groups of a (2 + 1)-dimensional Boiti-Leon-Pempinelli system. By using Ibragimov's method, the optimal system of one-dimensional subalgebras of this system is constructed. Truncated Painlevé analysis is used for deriving the Bäcklund transformation. The method of constructing lump-type solutions of integrable equations by means of Bäcklund transformation is first presented. Meanwhile, the lump-type solutions of the (2 + 1)-dimensional Boiti-Leon-Pempinelli system are obtained. The lump-type wave is one kind of rogue wave. The fusion-type N-solitary wave solutions are also constructed. In addition, this system is integrable in terms of the consistent Riccati expansion method.

Gross hematuria and urinary retention among men from a nationally representative survey in Sierra Leone.

PubMed

Patel, Hiten D; Kamara, Thaim B; Kushner, Adam L; Groen, Reinou S; Allaf, Mohamad E

2014-06-01

To estimate the prevalence of gross hematuria and urinary retention among men in Sierra Leone and report on barriers to care and associated disability. Gross hematuria and urinary retention are classic urologic complaints that require medical attention for significant underlying pathology, but their burden has not been quantified in a developing country. A cluster randomized, cross-sectional household survey was administered in Sierra Leone using the Surgeons OverSeas Assessment of Surgical need tool as a verbal head-to-toe examination. A total of 2 respondents in each of 25 households in 75 clusters were surveyed to assess surgical needs. Data on questions related to blood from the penis and the inability to urinate for men>12 years were included in the present analysis to determine the period and point prevalence of hematuria and urinary retention. From 3645 total respondents, 1054 (28.9%) were men>12 years included in the analysis. Period and point prevalence of gross hematuria were 21.8 per 1000 (95% confidence interval [CI] 13.0-30.7) and 12.3 per 1000 (95% CI 5.7-19.0), respectively, and for urinary retention, they were 19.9 per 1000 (95% CI 11.5-28.4) and 4.7 per 1000 (95% CI 0.5-8.9), respectively. Lack of financial resources was the major barrier to care. Disability assessment showed 19.1% were not able to work as a result of urinary retention, and 34.8% felt ashamed of their gross hematuria. The results provide a prevalence estimate of gross hematuria and urinary retention for men in Sierra Leone. Accessible medical and surgical care will be critical for early intervention and management. Copyright © 2014 Elsevier Inc. All rights reserved.

Technical efficiency of peripheral health units in Pujehun district of Sierra Leone: a DEA application

PubMed Central

Renner, Ade; Kirigia, Joses M; Zere, Eyob A; Barry, Saidou P; Kirigia, Doris G; Kamara, Clifford; Muthuri, Lenity HK

2005-01-01

Background The Data Envelopment Analysis (DEA) method has been fruitfully used in many countries in Asia, Europe and North America to shed light on the efficiency of health facilities and programmes. There is, however, a dearth of such studies in countries in sub-Saharan Africa. Since hospitals and health centres are important instruments in the efforts to scale up pro-poor cost-effective interventions aimed at achieving the United Nations Millennium Development Goals, decision-makers need to ensure that these health facilities provide efficient services. The objective of this study was to measure the technical efficiency (TE) and scale efficiency (SE) of a sample of public peripheral health units (PHUs) in Sierra Leone. Methods This study applied the Data Envelopment Analysis approach to investigate the TE and SE among a sample of 37 PHUs in Sierra Leone. Results Twenty-two (59%) of the 37 health units analysed were found to be technically inefficient, with an average score of 63% (standard deviation = 18%). On the other hand, 24 (65%) health units were found to be scale inefficient, with an average scale efficiency score of 72% (standard deviation = 17%). Conclusion It is concluded that with the existing high levels of pure technical and scale inefficiency, scaling up of interventions to achieve both global and regional targets such as the MDG and Abuja health targets becomes far-fetched. In a country with per capita expenditure on health of about US$7, and with only 30% of its population having access to health services, it is demonstrated that efficiency savings can significantly augment the government's initiatives to cater for the unmet health care needs of the population. Therefore, we strongly recommend that Sierra Leone and all other countries in the Region should institutionalise health facility efficiency monitoring at the Ministry of Health headquarter (MoH/HQ) and at each health district headquarter. PMID:16354299

The Impact of the West Africa Ebola Outbreak on Obstetric Health Care in Sierra Leone.

PubMed

Brolin Ribacke, Kim J; van Duinen, Alex J; Nordenstedt, Helena; Höijer, Jonas; Molnes, Ragnhild; Froseth, Torunn Wigum; Koroma, A P; Darj, Elisabeth; Bolkan, Håkon Angel; Ekström, AnnaMia

2016-01-01

As Sierra Leone celebrates the end of the Ebola Virus Disease (EVD) outbreak, we can begin to fully grasp its impact on already weak health systems. The EVD outbreak in West Africa forced many hospitals to close down or reduce their activity, either to prevent nosocomial transmission or because of staff shortages. The aim of this study is to assess the potential impact of EVD on nationwide access to obstetric care in Sierra Leone. Community health officers collected weekly data between January 2014-May 2015 on in-hospital deliveries and caesarean sections (C-sections) from all open facilities (public, private for-profit and private non-profit sectors) offering emergency obstetrics in Sierra Leone. This was compared to official data of EVD cases per district. Logistic and Poisson regression analyses were used to compute risk and rate estimates. Nationwide, the number of in-hospital deliveries and C-sections decreased by over 20% during the EVD outbreak. The decline occurred early on in the EVD outbreak and was mainly attributable to the closing of private not-for-profit hospitals rather than government facilities. Due to difficulties in collecting data in the midst of an epidemic, limitations of this study include some missing data points. Both the number of in-hospital deliveries and C-sections substantially declined shortly after the onset of the EVD outbreak. Since access to emergency obstetric care, like C-sections, is associated with decreased maternal mortality, many women are likely to have died due to the reduced access to appropriate care during childbirth. Future research on indirect health effects of health system breakdown should ideally be nationwide and continue also into the recovery phase. It is also important to understand the mechanisms behind the deterioration so that important health services can be reestablished.

Traumatic Injuries in Developing Countries: Report from a Nationwide Cross-Sectional Survey of Sierra Leone

PubMed Central

Stewart, Kerry-Ann; Groen, Reinou S.; Kamara, Thaim B.; Farahzard, Mina; Samai, Mohamed; Yambasu, Sahr E.; Cassidy, Laura D.; Kushner, Adam L.; Wren, Sherry M.

2014-01-01

Objective Despite the tremendous disability and mortality caused by traumatic injuries worldwide, there is a relative dearth of information on the burden of injuries in developing countries. In an effort to document the surgical burden of disease in Sierra Leone, a nationwide survey was conducted utilizing the Surgeons OverSeas Assessment of Surgical Need (SOSAS) tool. Here, we report the injury data from this study with the aim to (1) provide an estimate of injury prevalence, (2) determine the mechanisms of injury, and (3) evaluate the degree of injury related deaths. Methods A population-based household survey was conducted in Sierra Leone in 2012. Participants were selected using a two-stage random sampling method, which generated a target population of 3750 participants across the 14 districts of Sierra Leone. Frequency distributions of mechanisms of injury based on age, sex, and urban versus rural residence were computed, and bivariate logistic regression models used to determine associations between sociodemographic factors and injury patterns. Results Data was analyzed from 1,843 households and 3,645 respondents, representing a response rate of 98.3%. Four hundred and fifty-two respondents (12.4%) reported at least one traumatic injury in the preceding year. Falls were the most common cause of non-fatal injuries, accounting for over 40% of injuries. The extremities were most commonly injured (55% of injuries) regardless of age or sex. Although motor vehicle related injuries were the 4th most common cause of injury overall, they were the leading cause of injury related deaths, accounting for almost 6% of fatal injuries. Conclusion This study provides baseline data on the burden of traumatic injuries in one of the world's poorest nations. In addition to injury prevention measures, immediate strategies to address current healthcare deficits are urgently needed in these resource poor areas. This report is an Original Article with Level I evidence. PMID:23325317

Stimulated Brillouin scattering in the field of a two-dimensionally localized pumping wave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solikhov, D. K., E-mail: davlat56@mail.ru; Dvinin, S. A., E-mail: dvinin@phys.msu.ru

2016-06-15

Stimulated Brillouin scattering of electromagnetic waves in the field of a two-dimensionally localized pump wave at arbitrary scattering angles in the regime of forward scattering is analyzed. Spatial variations in the amplitudes of interacting waves are studied for different values of the pump field and different dimensions of the pump wave localization region. The intensity of scattered radiation is determined as a function of the scattering angle and the dimensions of the pump wave localization region. It is shown that the intensity increases with increasing scattering angle.

Probing near-normally propagating bulk acoustic waves using pseudo-reflection geometry Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Parsons, L. C.; Andrews, G. T.

2012-09-01

Pseudo-reflection geometry Brillouin spectroscopy can be used to probe acoustic wave dispersion approximately along the surface normal of a material system while avoiding the difficulties associated with specularly reflected light encountered in an ideal reflection configuration. As an example of its application, we show analytically that it can be used to determine both the refractive index and bulk acoustic mode velocities of optically-isotropic non-metallic materials and confirm the utility of the approach via a series of experiments on fused quartz, gallium phosphide, water, and porous silicon films.

Brillouin-scattering measurements of surface-acoustic-wave velocities in silicon at high temperatures

NASA Astrophysics Data System (ADS)

Stoddart, P. R.; Comins, J. D.; Every, A. G.

1995-06-01

Brillouin-scattering measurements of the angular dependence of surface-acoustic-wave velociites at high temperatures are reported. The measurements have been performed on the (001) surface of a silicon single crystal at temperatures up to 800 °C, allowing comparison of the results with calculated velocities based on existing data for the elastic constants and thermal expansion of silicon in this temperature range. The change in surface-acoustic-wave velocity with temperature is reproduced well, demonstrating the value of this technique for the characterization of the high-temperature elastic properties of opaque materials.

Prévalence des dyslipidémies au laboratoire de biochimie du CHU Aristide le Dantec de Dakar, Sénégal

PubMed Central

Cissé, Fatou; Agne, Fatou Diallo; Diatta, Alassane; Mbengue, Abdou Salam; Ndiaye, Arame; Samba, Abdourahmane; Thiam, Souleymane; Doupa, Dominique; Sarr, Gaston Ndéné; Sall, Niama Diop; Touré, Méissa

2016-01-01

Introduction L'objectif de cette étude était d'évaluer la prévalence des dyslipidémies chez les patients reçus au laboratoire de Biochimie de l'Hôpital Aristide Le Dantec pour le dosage d'un paramètre lipidique au cours de l'année 2013. Méthodes Il s'agit d'une étude rétrospective portant sur 1356 patients âgés de 10 à 94 ans reçus au laboratoire de Biochimie du CHU Le Dantec de janvier à décembre 2013. Etaient inclus dans l'étude, tous les patients ayant au moins un paramètre du bilan lipidique dont les résultats étaient enregistrés dans le registre du laboratoire. Le cholestérol total, le cholestérol HDL, le cholestérol LDL ainsi que les triglycérides ont été dosés grâce à des méthodes enzymatiques sur un automate de Biochimie de type Cobas Integra 400 (Roche Diagnostics). Résultats La prévalence des dyslipidémies dans notre population d'étude est de 39,30%. Les prévalences de l'hypercholestérolémie, l'hypoHDLémie, l'hyperLDLémie, l'hypertriglycéridémie et l'hyperlipidémie mixte étaient respectivement : 30,89% ; 7,30% ; 31,19% ; 0,51% ; 7,22%. Les sujets de 40 à 59 ans semblaient être plus exposés et on note une prédominance féminine en ce qui concerne l'hypercholestérolémie (54,17% vs 45,82%), l'hypoHDLémie (54,54% vs45, 45%), et l'hyperlipidémie mixte (51,08% vs 48,97%). Enfin les dyslipidémies étaient fortement corrélées à l'HTA et l'obésité. Conclusion La forte prévalence des dyslipidémies retrouvée dans notre étude démontre l'intérêt d'étudier la prévalence des facteurs de risque cardio-vasculaires en particulier les dyslipidémies dans la population sénégalaise. PMID:28292030

[Western area surge for controlling Ebola hemorrhagic fever outbreak in Sierra Leone and evaluation of its effect].

PubMed

Chen, Yong; Wu, Dan; Zhang, Wenyi; Chen, Zeliang; Chang, Guohui; Tian, Shuguang; Yang, Ruifu; Liu, Chao

2015-10-01

To investigate the Western Area Surge (WAS) program in the Ebola outbreak of Sierra Leone, and to analyze its implementing effect. The subject of this study was 3,813 laboratory confirmed Ebola hemorrhagic fever (EHF) cases reported in Sierra Leone from November 19, 2014 through January 27, 2015, a period before and after the implementation of the WAS program. To analyze and make conclusions according to the working experience of China Mobile Laboratory Reponses Team in the fight of Ebola outbreak, using WHO published EHF case definition to make diagnosis and compare the number of bed numbers, confirmed EHF cases, samples tested, and positive rates before and after implementation of WAS program. From the implementation of WAS program on 17th December 2014 to half a month later, the total numbers of Ebola holding and treatment centers increased from 640 to 960, six additional laboratories were established. On January, 2015, another two laboratories from America and The Netherlands were established. The numbers of samples tested one month before and after WAS program were 7,891 and 9,783, respectively, with an increase of 24.0 percent, while the positive rate of Ebola virus decreased from 22.2% (1,752/7,891) to 11.0% (1,077/9,783). The positive rate of blood samples decreased from 39.6% (248/626) in the month before WAS program to 27.4% (131/478) (χ2=17.93, P<0.001) in the mother after WAS program, the positive rate of blood samples 22.7% (103/454) to 10% (62/609) (χ2=31.03, P<0.001), accordingly. After 3 weeks of WAS program, in addition to Western Area, another four hotspots in Sierra Leone had also reported a significant decrease of the numbers of confirmed EVD cases. Forty-two days after implementation of WAS program, the daily number of laboratory confirmed EHF cases decreased from 63 to 10. WAS program played a vital role in controlling the EHF outbreak rapidly in Sierra Leone. It could also provide guidance for the control similar large infectious diseases

Amplification of a seed pumped by a chirped laser in the strong coupling Brillouin regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schluck, F.; Lehmann, G.; Spatschek, K. H.

Seed amplification via Brillouin backscattering of a long pump laser-pulse is considered. The interaction takes place in the so called strong coupling regime. Pump chirping is applied to mitigate spontaneous Raman backscattering of the pump before interacting with the seed. The strong coupling regime facilitates stronger exponential growth and narrower seeds compared to the so called weak coupling regime, although in the latter the scaling with pump amplitude is stronger. Strong coupling is achieved when the pump laser amplitude exceeds a certain threshold. It is shown how the chirp influences both the linear as well as the nonlinear amplification process.more » First, linear amplification as well as the seed profiles are determined in dependence of the chirping rate. In contrast to the weak coupling situation, the evolution is not symmetric with respect to the sign of the chirping rate. In the nonlinear stage of the amplification, we find an intrinsic chirp of the seed pulse even for an un-chirped pump. We show that chirping the pump may have a strong influence on the shape of the seed in the nonlinear amplification phase. Also, the influence of pump chirp on the efficiency of Brillouin seed amplification is discussed.« less

Treatment Seeking and Ebola Community Care Centers in Sierra Leone: A Qualitative Study.

PubMed

Carter, Simone E; O'Reilly, Marion; Frith-Powell, Jack; Umar Kargbo, Alpha; Byrne, Daniel; Niederberger, Eva

2017-01-01

Ebola Treatment Units were able to provide only 60% of necessary treatment beds in Sierra Leone. As a result, the Government of Sierra Leone decided to construct Community Care Centers. These were intended to increase treatment-seeking behavior and reduce the community-level spread of Ebola by facilitating access to care closer to communities. Through qualitative data collection in 3 districts, this study seeks to understand the perceived impact that proximity to such Centers had on treatment-seeking behavior. Feedback from community members and Community Health Volunteers indicates that proximity to treatment reduced fears, especially those arising from the use of ambulances, lack of familiarity with medical Centers, and loss of contact with family members taken for treatment. Participants report that having a Center close to their home enables them to walk to treatment and witness survivors being discharged. Living close to Centers also enables communities to be involved in their design and daily operation, helping to build trust in them as acceptable treatment facilities. Further research is required to understand the appropriate design, operation, and epidemiological impact of Centers. Further investigation should incorporate the effect of an outbreak's severity and the stage (duration) of the outbreak on potential acceptance of Centers.

Performance Investigation of Millimeter Wave Generation Reliant on Stimulated Brillouin Scattering

NASA Astrophysics Data System (ADS)

Tickoo, Sheetal; Gupta, Amit

2018-04-01

In this work, photonic method of generating the millimeter waves has been done based on Brillouin scattering effect in optical fiber. Here different approaches are proposed to get maximum frequency shift in mm-wave region using only pumps, radio signals with Mach-Zehnder modulator. Moreover for generated signal validation, signals modulated and send to both wired and wireless medium in optical domain. It is observed that maximum shift of 300 GHz is realized using 60 GHz input sine wave. Basically a frequency doubler is proposed which double shift of input frequency and provide better SNR. For the future generation network system, the generation of millimeter waves makes them well reliable for the transmission of the data.

Visualising higher order Brillouin zones with applications

NASA Astrophysics Data System (ADS)

Andrew, R. C.; Salagaram, T.; Chetty, N.

2017-05-01

A key concept in material science is the relationship between the Bravais lattice, the reciprocal lattice and the resulting Brillouin zones (BZ). These zones are often complicated shapes that are hard to construct and visualise without the use of sophisticated software, even by professional scientists. We have used a simple sorting algorithm to construct BZ of any order for a chosen Bravais lattice that is easy to implement in any scientific programming language. The resulting zones can then be visualised using freely available plotting software. This method has pedagogical value for upper-level undergraduate students since, along with other computational methods, it can be used to illustrate how constant-energy surfaces combine with these zones to create van Hove singularities in the density of states. In this paper we apply our algorithm along with the empirical pseudopotential method and the 2D equivalent of the tetrahedron method to show how they can be used in a simple software project to investigate this interaction for a 2D crystal. This project not only enhances students’ fundamental understanding of the principles involved but also improves transferable coding skills.

[Establishment of Quality Control System of Nucleic Acid Detection for Ebola Virus in Sierra Leone-China Friendship Biological Safety Laboratory].

PubMed

Wang, Qin; Zhang, Yong; Nie, Kai; Wang, Huanyu; Du, Haijun; Song, Jingdong; Xiao, Kang; Lei, Wenwen; Guo, Jianqiang; Wei, Hejiang; Cai, Kun; Wang, Yanhai; Wu, Jiang; Gerald, Bangura; Kamara, Idrissa Laybohr; Liang, Mifang; Wu, Guizhen; Dong, Xiaoping

2016-03-01

The quality control process throughout the Ebola virus nucleic acid detection in Sierra Leone-China Friendship Biological Safety Laboratory (SLE-CHN Biosafety Lab) was described in detail, in order to comprehensively display the scientific, rigorous, accurate and efficient practice in detection of Ebola virus of first batch detection team in SLE-CHN Biosafety Lab. Firstly, the key points of laboratory quality control system was described, including the managements and organizing, quality control documents and information management, instrument, reagents and supplies, assessment, facilities design and space allocation, laboratory maintenance and biosecurity. Secondly, the application of quality control methods in the whole process of the Ebola virus detection, including before the test, during the test and after the test, was analyzed. The excellent and professional laboratory staffs, the implementation of humanized management are the cornerstone of the success; High-level biological safety protection is the premise for effective quality control and completion of Ebola virus detection tasks. And professional logistics is prerequisite for launching the laboratory diagnosis of Ebola virus. The establishment and running of SLE-CHN Biosafety Lab has landmark significance for the friendship between Sierra Leone and China, and the lab becomes the most important base for Ebola virus laboratory testing in Sierra Leone.

"Farming Miners" or "Mining Farmers"?: Diamond Mining and Rural Development in Post-Conflict Sierra Leone

ERIC Educational Resources Information Center

Maconachie, Roy; Binns, Tony

2007-01-01

Sierra Leone is currently emerging from a brutal civil war that lasted most of the 1990s, and now has the dubious distinction of being ranked among the world's poorest countries. As thousands of displaced people move back to their villages, a large proportion of the predominantly farm-based rural population are growing food crops for the first…

Sierra Leone's Former Child Soldiers: A Follow-Up Study of Psychosocial Adjustment and Community Reintegration

ERIC Educational Resources Information Center

Betancourt, Theresa Stichick; Borisova, Ivelina Ivanova; Williams, Timothy Philip; Brennan, Robert T.; Whitfield, Theodore H.; de la Soudiere, Marie; Williamson, John; Gilman, Stephen E.

2010-01-01

This is the first prospective study to investigate psychosocial adjustment in male and female former child soldiers (ages 10-18; n = 156, 12% female). The study began in Sierra Leone in 2002 and was designed to examine both risk and protective factors in psychosocial adjustment. Over the 2-year period of follow-up, youth who had wounded or killed…

[Social and economic impact of chicken pox vaccine at 15 months of age. Castile and Leon, Spain, 2004].

PubMed

Pérez-Rubio, A; Castrodeza Sanz, J J; Gil Costa, M; Luquero Alcalde, F J; Eiros Bouza, J; Ortiz de Lejarazu, R

2008-01-01

Chicken pox is a mainly childhood contagious disease caused by the Varicella Zoster Virus which gives rise to major healthcare and social costs. In 2005, Castile and Leon added chicken pox vaccine injections to its childhood vaccination schedule for eleven year-olds subject to coming down with this disease. This strategy does not modify the major mobility generated thereby at younger ages. This study is aimed at evaluating the profitability of systematic vaccination for chicken pox in infants 15 months of age in Castile and Leon. An economic cost-benefit evaluation has been set out by jeans of a decision-making tree. A fictitious cohort of 100,000 children in Castile and Leon having reached 15 months of age in 2004 is studied, to whom the chicken pox vaccine would be administered in conjunction with the mumps, measles, rubella vaccines. This study is approached from the social standpoint. The time horizon selected was that of up until the study cohort was to reach 15 years of age, applying a 3% discount rate. A sensitivity analysis was made for evaluating the uncertainty of some variables... The cost-benefit ratio of adding this vaccine to the childhood vaccination schedule amounts to 1.23. From the social standpoint, administering chicken pox vaccine in conjunction with the mumps, measles, rubella vaccines show itself to be profitable. The profitability is modified both if a second dose of vaccine is added as well as if only the direct healthcare costs are analyzed.

School Persistence in the Wake of War: Wartime Experiences, Reintegration Supports, and Dropout in Sierra Leone

ERIC Educational Resources Information Center

Zuilkowski, Stephanie Simmons; Betancourt, Theresa S.

2014-01-01

This article examines the relationship of wartime experience and reintegration supports to students' risk of school dropout. It draws on longitudinal, mixed-methods data collected among children and youth in Sierra Leone from 2002 through 2008. The study finds that family financial support and perceived social support are positively associated…

Phase-based, high spatial resolution and distributed, static and dynamic strain sensing using Brillouin dynamic gratings in optical fibers.

PubMed

Bergman, Arik; Langer, Tomi; Tur, Moshe

2017-03-06

A novel technique combining Brillouin phase-shift measurements with Brillouin dynamic gratings (BDGs) reflectometry in polarization-maintaining fibers is presented here for the first time. While a direct measurement of the optical phase in standard BDG setups is impractical due to non-local phase contributions, their detrimental effect is reduced by ~4 orders of magnitude through the coherent addition of Stokes and anti-Stokes reflections from two counter-propagating BDGs in the fiber. The technique advantageously combines the high-spatial-resolution of BDGs reflectometry with the increased tolerance to optical power fluctuations of phasorial measurements, to enhance the performance of fiber-optic strain sensors. We demonstrate a distributed measurement (20cm spatial-resolution) of both static and dynamic (5kHz of vibrations at a sampling rate of 1MHz) strain fields acting on the fiber, in good agreement with theory and (for the static case) with the results of commercial reflectometers.

Single-crystal elastic properties of aluminum oxynitride (AlON) from brillouin scattering

DOE PAGES

Satapathy, Sikhanda; Ahart, Muhtar; Dandekar, Dattatraya; ...

2016-01-19

The Brillouin light-scattering technique was used to determine experimentally the three independent elastic constants of cubic aluminum oxynitride at the ambient condition. They are C 11=334.8(±1.8) GPa, C 12=164.4(± 1.2) GPa, and C 44=178.6(± 1.1) GPa. Its bulk modulus is 221.2 GPa. The magnitude of Zener anisotropic ratio is 2.1 similar to other spinels. Here, the anisotropic nature of the material is shown by a large variation in the Young’s modulus and Poisson’s ratio with crystallographic directions. The material was found to be auxetic in certain orientations.

Brillouin Light Scattering study of Fe/Pd multilayers

NASA Astrophysics Data System (ADS)

From, Milton; Cheng, Li; Altounian, Zaven

2002-03-01

We have performed a series of Brillouin light scattering (BLS) measurements on sputtered multilayers in order to test a recent calculation[1] that predicts that the majority of spin-wave modes present in a magnetic multilayer will not be seen by BLS due to destructive interference between light scattered by different layers in the structure. We have measured the BLS spectra of a series of Si(100) + Pdx + [Fe/Pdx] x 25 sputtered multilayers. The thickness of the Fe layers was 1.5 nm and the Pd thicknesses examined were x = 0.5nm, 1.0nm, 1.5nm, 2.5nm, and 4.0nm. The BLS instrument used was a 4-pass Fabry-Perot interferometer operated in the back-scattering geometry with 514.5 nm laser light. We obtain good 2-parameter fits of the model calculation to the data for all values of Pd thickness and for applied magnetic fields in the range 0 < H < 0.7 T. [1]J.F. Cochran, Phys Rev B, vol. 64, 134406 (2001)

Brillouin lasing in single-mode tapered optical fiber with inscribed fiber Bragg grating array

NASA Astrophysics Data System (ADS)

Popov, S. M.; Butov, O. V.; Chamorovskiy, Y. K.; Isaev, V. A.; Kolosovskiy, A. O.; Voloshin, V. V.; Vorob'ev, I. L.; Vyatkin, M. Yu.; Mégret, P.; Odnoblyudov, M.; Korobko, D. A.; Zolotovskii, I. O.; Fotiadi, A. A.

2018-06-01

A tapered optical fiber has been manufactured with an array of fiber Bragg gratings (FBG) inscribed during the drawing process. The total fiber peak reflectivity is 5% and the reflection bandwidth is ∼3.5 nm. A coherent frequency domain reflectometry has been applied for precise profiling of the fiber core diameter and grating reflectivity both distributed along the whole fiber length. These measurements are in a good agreement with the specific features of Brillouin lasing achieved in the semi-open fiber cavity configuration.

Hybrid Raman/Brillouin-optical-time-domain-analysis-distributed optical fiber sensors based on cyclic pulse coding.

PubMed

Taki, M; Signorini, A; Oton, C J; Nannipieri, T; Di Pasquale, F

2013-10-15

We experimentally demonstrate the use of cyclic pulse coding for distributed strain and temperature measurements in hybrid Raman/Brillouin optical time-domain analysis (BOTDA) optical fiber sensors. The highly integrated proposed solution effectively addresses the strain/temperature cross-sensitivity issue affecting standard BOTDA sensors, allowing for simultaneous meter-scale strain and temperature measurements over 10 km of standard single mode fiber using a single narrowband laser source only.

Time-Dependent Modeling of Brillouin Scattering in Optical Fibers Excited by a Chirped Diode Laser

DTIC Science & Technology

2012-10-31

backscattering. To demonstrate this effect, we simulated an ytterbium -cladding- doped fiber with length L = 18 m and modal radius r = 13.75 μm at a...The resulting SBS suppression is well described by an adiabatic model and agrees with experimental results. For an 18-m active fiber pumped at 1.06...8] R. B. Jenkins, R. M. Sova, and R. I. Joseph, “Steady-state noise analysis of spontaneous and stimulated Brillouin scattering in optical fibers

Marginalization of girl mothers during reintegration from armed groups in Sierra Leone.

PubMed

Burman, M E; McKay, S

2007-12-01

Although the widespread presence of girls who participate in fighting forces is increasingly recognized, they remain a highly marginalized group globally, receiving little attention either during or after armed conflict. This is especially true for "girl mothers," girls who return to communities with children born while members of fighting forces. The concept of marginalization (Hall et al. 1994) is used to examine what happens to girl soldiers, especially girl mothers, in the aftermath of armed conflict when they seek to reintegrate back into their communities. This analysis, as part of a larger study of reintegration of girl mothers, is based on field work with girls who were in fighting forces in northwest Sierra Leone, especially those who returned with children. The type and level of marginalization these girls experience is consistent with the conceptualization of marginalization; however, they lack voice and experience shame and vulnerability. Moreover, economics were fundamentally related to their marginalization. The girls' access to resources was significantly constrained because the area was heavily impacted by the war and because of widespread poverty throughout Sierra Leone. The findings raise important questions about marginalization of girls affected by war. Girls and girl mothers experience an extremely high level of marginalization; however, some aspects are not consistent with the original conceptualization of marginalization. Theory development in nursing needs to incorporate multiple voices, especially those of the very marginalized and be done in such a manner that benefits and empowers.

Dynamical properties in supercooling liquid of trehalose aqueous solution studied by Brillouin scattering

NASA Astrophysics Data System (ADS)

Shibata, Tomohiko; Tominaga, Ayane; Takayama, Haruki; Kojima, Seiji

2013-02-01

Brillouin scattering spectroscopy has been applied to study the dynamical properties of glass transition of trehalose aqueous solutions in a high-frequency gigahertz range and in the temperature range (-190°C ≤ T ≤ 100°C). The temperature variations of sound velocity and attenuation were accurately determined using the refractive index measured by a prism-coupling method. The temperature dependence of relaxation time of the structural relaxation process was determined by the Debye model. Its temperature dependence shows Arrhenius behavior in a liquid state. The parameters of Arrhenius law were also determined as a function of trehalose concentration.

Brillouin light scattering study of Fe 15 Å /Pd x multilayers

NASA Astrophysics Data System (ADS)

From, M.; Cheng, Li; Altounian, Zaven

2004-03-01

Brillouin light scattering (BLS) measurements have been carried out on a series of sputtered Fe/Pd multilayers. The Fe thickness in all samples was 15 Å and the Pd spacer thickness ranged from 6 to 43 Å. We compared the composition and magnetic field dependence of the BLS spectra with a single parameter fit of a new BLS model calculation by John Cochran (Phys. Rev. B 64 (2001) 134406). The data are consistent with a surface anisotropy fit parameter of KS=0.35±0.05 ergs/cm 2 except at the thinnest Pd thickness where it is perhaps not surprising that there is some discrepancy with the model since it assumes zero intermixing between the Fe and Pd layers.

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leon reservoirs, Chihuahua, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Méndez-García, C.; Montero-Cabrera, M. E., E-mail: elena.montero@cimav.edu.mx; Renteria-Villalobos, M.

2008-01-01

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. ²³²Th-series, ²³⁸U-series, ⁴⁰K and ¹³⁷Cs activity concentrations (AC, Bq kg⁻¹) were determined by gamma spectrometry with a high purity Ge detector. ²³⁸U and ²³⁴U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating ofmore » core sediments was performed applying CRS method to ²¹⁰Pb activities. Results were verified by ¹³⁷Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High ²³⁸U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento – Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) ²³⁴U/²³⁸U and ²³⁸U/²²⁶Ra in sediments have values between 0.9–1.2, showing a behavior close to radioactive equilibrium in the entire basin. ²³²Th/²³⁸U, ²²⁸Ra/²²⁶Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs.« less

Rural-Urban Migration in Sierra Leone: Determinants and Policy Implications. African Rural Economy Paper No. 13.

ERIC Educational Resources Information Center

Byerlee, Derek; And Others

Study objectives were to: increase the understanding of rural to urban migration processes in Africa and Sierra Leone; develop and test a theoretical schema and survey methodology for migration research; and evaluate the effects of policy on migration. The migration survey was conducted in rural areas, urban areas, and again in the rural areas…

Situation Report--Algeria, Bangladesh, Fiji, Gilbert and Ellice Islands, Iran, Jordan, New Zealand, Rwanda, and Sierra Leone.

ERIC Educational Resources Information Center

International Planned Parenthood Federation, London (England).

Data relating to population and family planning in nine foreign countries are presented in these situation reports. Countries included are Algeria, Bangledesh, Fiji, Gilbert and Ellice Islands, Iran, Jordan, New Zealand, Rwanda, and Sierra Leone. Information is provided under two topics, general background and family planning situation, where…

1200°C high-temperature distributed optical fiber sensing using Brillouin optical time domain analysis.

PubMed

Xu, Pengbai; Dong, Yongkang; Zhou, Dengwang; Fu, Cheng; Zhang, Juwang; Zhang, Hongying; Lu, Zhiwei; Chen, Liang; Bao, Xiaoyi

2016-07-20

In this paper, up to 1100°C and 1200°C high-temperature distributed Brillouin sensing based on a GeO₂-doped single-mode fiber (SMF) and a pure silica photonic crystal fiber (PCF) are demonstrated, respectively. The Brillouin frequency shift's (BFS) dependence on temperatures of the SMF and PCF agrees with a nonlinear function instead of a linear function, which is mainly due to the change of the acoustic velocity in a silica fiber. BFS hopping is observed in both kinds of fibers between 800°C-900°C in the first annealing process, and after that, the BFS exhibits stability and repeatability with a measurement accuracy as high as ±2.4°C for the SMF and ±3.6°C for the PCF. The BFS hopping is a highly temperature-dependent behavior, which means that a high temperature (>800°C) would accelerate this process to reach a stable state. After BFS hopping, both the SMF and PCF show good repeatability for temperatures higher than 1000°C without annealing. The process of coating burning of a silica fiber not only introduces a loss induced by micro-bending, but also imposes a compressive stress on the bare fiber, which contributes to an additional BFS variation at the temperature period of the coating burning (∼300°C-500°C).

Rapid assessment of knowledge, attitudes, practices, and risk perception related to the prevention and control of Ebola virus disease in three communities of Sierra Leone.

PubMed

Jiang, Hai; Shi, Guo-Qing; Tu, Wen-Xiao; Zheng, Can-Jun; Lai, Xue-Hui; Li, Xin-Xu; Wei, Qiang; Li, Mei; Deng, Li-Quan; Huo, Xiang; Chen, Ming-Quan; Xu, Feng; Ye, Long-Jie; Bai, Xi-Chen; Chen, Tong-Nian; Yin, Shao-Hua; Samba, Thomas T; Liang, Xiao-Feng

2016-06-06

The recent outbreak of the Ebola virus disease (EVD) in Sierra Leone has been characterized by the World Health Organization as one of the most challenging EVD outbreaks to date. The first confirmed case in Sierra Leone was a young woman who was admitted to a government hospital in Kenema following a miscarriage on 24 May 2014. On 5 January 2015, intensified training for an EVD response project was initiated at the medical university of Sierra Leone in Jui. To understand the knowledge, attitudes, practices, and perceived risk of EVD among the public, especially after this training, a rapid assessment was conducted from 10 to 16 March 2015. Interviews were conducted with 466 participants based on questionnaires that were distributed from 10 to 16 March 2015 by cluster sampling in three adjacent communities, namely Jui, Grafton, and Kossoh Town, in the Western Area Rural District of Sierra Leone. It was found that knowledge about EVD was comprehensive and high. Positive attitude towards prevention was found to be satisfactory. Nearly all participants knew the reporting phone number 117 and had reported some change in behavior since learning about Ebola. More than half (62 %) of the participants had a history of travelling to urban areas, which increases the risk of infection. The multivariable logistic regression analysis showed that community and occupation were variables associated with perceived risk of EVD. Our study showed that community level social mobilization and community engagement were an effective strategy in the special context.

Laser beam combining and cleanup by stimulated Brillouin scattering in a multimode optical fiber.

PubMed

Rodgers, B C; Russell, T H; Roh, W B

1999-08-15

A new technique for combining low-power laser beams has been demonstrated by use of semiconductor diode lasers. The technique, which is appropriate for any single-longitudinal-mode laser, is based on stimulated Brillouin scattering (SBS) in long multimode optical fibers. It produces a clean Gaussian-like beam that corresponds to the fundamental fiber mode, irrespective of the profile of the pump. Coherent as well as incoherent combining was demonstrated, and conversion slope efficiencies as high as 67% and 83% were shown to be achievable for the single-pass and ring-cavity SBS geometries, respectively.

Evaluating the use of cell phone messaging for community Ebola syndromic surveillance in high risked settings in Southern Sierra Leone.

PubMed

Jia, Kangbai; Mohamed, Koroma

2015-09-01

Most underdeveloped countries do not meet core disease outbreak surveillance because of the lack of human resources, laboratory and infrastructural facilities. The use of cell phone technology for disease outbreak syndromic surveillance is a new phenomenon in Sierra Leone despite its successes in other developing countries like Sri Lanka. In this study we set to evaluate the effectiveness of using cell phone technology for Ebola hemorrhagic fever syndromic surveillance in a high risked community in Sierra Leone. This study evaluated the effectiveness of using cell phone messaging (text and calls) for community Ebola hemorrhagic fever syndromic surveillance in high risked community in southern Sierra Leone. All cell phone syndromic surveillance data used for this study was reported as cell phone alert messages-texts and voice calls; by the Moyamba District Health Management Team for both Ebola hemorrhagic fever suspect and mortalities. We conducted a longitudinal data analysis of the monthly cumulative confirmed Ebola hemorrhagic fever cases and mortalities collected by both the traditional sentinel and community cell phone syndromic surveillance from August 2014 to October 2014. A total of 129 and 49 Ebola hemorrhagic fever suspect and confirmed cases respectively were recorded using the community Ebola syndromic surveillance cell phone alert system by the Moyamba District Health Management Team in October 2014. The average number of Ebola hemorrhagic fever suspects and confirmed cases for October 2014 were 4.16 (Std.dev 3.76) and 1.58 (Std.dev 1.43) respectively. Thirty-four percent (n=76) of the community Ebola syndromic surveillance cell phone alerts that were followed-up within 24 hours reported Ebola hemorrhagic fever suspect cases while 65.92% (n=147) reported mortality. Our study suggests some form of underreporting by the traditional sentinel Ebola hemorrhagic fever disease surveillance system in Moyamba District southern Sierra Leone for August

Food Deserts in Leon County, FL: Disparate Distribution of Supplemental Nutrition Assistance Program-Accepting Stores by Neighborhood Characteristics

ERIC Educational Resources Information Center

Rigby, Samantha; Leone, Angela F.; Kim, Hwahwan; Betterley, Connie; Johnson, Mary Ann; Kurtz, Hilda; Lee, Jung Sun

2012-01-01

Objective: Examine whether neighborhood characteristics of racial composition, income, and rurality were related to distribution of Supplemental Nutrition Assistance Program (SNAP)-accepting stores in Leon County, Florida. Design: Cross-sectional; neighborhood and food store data collected in 2008. Setting and Participants: Forty-eight census…

Brillouin scattering in planar waveguides. II. Experiments

NASA Astrophysics Data System (ADS)

Chiasera, A.; Montagna, M.; Moser, E.; Rossi, F.; Tosello, C.; Ferrari, M.; Zampedri, L.; Caponi, S.; Gonçalves, R. R.; Chaussedent, S.; Monteil, A.; Fioretto, D.; Battaglin, G.; Gonella, F.; Mazzoldi, P.; Righini, G. C.

2003-10-01

Silica-titania planar waveguides of different thicknesses and compositions have been produced by radio-frequency sputtering and dip coating on silica substrates. Waveguides were also produced by silver exchange on a soda-lime silicate glass substrate. Brillouin scattering of the samples has been studied by coupling the exciting laser beam with a prism to different transverse-electric (TE) modes of the waveguides, and collecting the scattered light from the front surface. In multimode waveguides, the spectra depend on the m mode of excitation. For waveguides with a step index profile, two main peaks due to longitudinal phonons are present, apart from the case of the TE0 excitation, where a single peak is observed. The energy separation between the two peaks increases with the mode index. In graded-index waveguides, m-1 peaks of comparable intensities are observed. The spectra are reproduced very well by a model which considers the space distribution of the exciting field in the mode, a simple space dependence of the elasto-optic coefficients, through the value of the refraction index, and neglects the refraction of phonons. A single-fit parameter, i.e., the longitudinal sound velocity, is used to calculate as many spectra as is the number of modes in the waveguide.

Learning Styles and Attitudes toward Online Education in Four Universities in the State of Nuevo Leon, Mexico

ERIC Educational Resources Information Center

Martinez de Monarrez, Patricia; Korniejczuk, Victor

2013-01-01

The purpose of this research was to find the relation-ship between the predominant learning styles among university online students and their attitude toward online education. Data were collected from 385 students enrolled in undergraduate and graduate programs from four universities in the state of Nuevo Leon, Mexico. Significant effects of…

Assessment on the Knowledge and Reported Practices of Women on Maternal and Child Health in Rural Sierra Leone: A Cross-Sectional Survey

PubMed Central

Kanu, Joseph Sam; Tang, Yuan; Liu, Yawen

2014-01-01

Background Globally, Sierra Leone is ranked among the countries with the worst maternal and child health indicators. The mortality of women and children is significantly higher compared with other developing countries. The death of women and children can be prevented by simple cost-effective community-based interventions. The aim of this present study was to learn the knowledge levels of women on maternal and child health, and treatment-seeking and preventive behaviours in rural Sierra Leone and provide appropriate suggestions for policy makers. Moreover, the study also aimed to evaluate the effect of a husband’s involvement on health knowledge and practices of women in rural Sierra Leone. Methods Women with at least a child of five years or below were interviewed in their households through a structured questionnaire. Characteristics of the households and of the respondents were collected and the number of correct answers given to the health knowledge and practice questions and their percentage distributions were tabulated and an overall health knowledge score was calculated. Results The mean score of the derived overall health-related knowledge was 61.6% (maximum of 91% and a minimum of 18%) with a standard deviation of 14.7% and a median of 63.3%. Multivariable regression analyses showed education and number of pregnancies are associated with knowledge score, with significantly improved health knowledge scores amongst those who accessed higher education. There were some inappropriate practices in hygiene and sanitation. However, vaccination coverage was high with almost 100% coverage for BCG. Conclusions Based on the findings of this study, women’s knowledge on maternal and child health care are inadequate in rural Sierra Leone. Health promotion activities focusing on prevention of diarrhoea, malaria and pneumonia, improvement in health-related knowledge on pregnancy, delivery, neonatal care and environmental sanitation would be invaluable. PMID:25166504

Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

NASA Astrophysics Data System (ADS)

Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

2015-02-01

Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons.

Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo

2015-02-02

Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in ordermore » to evaluate their potential use as temperature sensors for acoustic phonons.« less

[Non-invasive, spatially resolved determination of tissue properties of the crystalline lens with regard to rheology, refractive index, density and protein concentration by using Brillouin spectroscopy].

PubMed

Reiss, S; Stachs, O; Guthoff, R; Stolz, H

2011-12-01

The confocal Brillouin spectroscopy is an innovative measurement method that allows the non-invasive determination of the rheological properties of materials. Its application in ophthalmology can offer the possibility to determine in-vivo the deformation properties of sections of transparent biological tissue such as the cornea or eye lens with spatial resolution. This seems to be a promising approach concerning current presbyopia research. Due to the spatially resolved detection of the viscoelastic lens properties, a better understanding of the natural aging process of the lens and the influences of different lens opacities on the stiffness is expected. From the obtained spectral data the relative protein levels, the relative refractive index profile and the relative density profile within the lens tissue can be derived in addition. A measurement set-up for confocal Brillouin microscopy based on spectral analysis of spontaneous Brillouin scattering signals by using a high-resolution dispersive device is presented. First in-vitro test results on animal and human lenses are presented and evaluated concerning their rheological significance. These data are compared with known research results. © Georg Thieme Verlag KG Stuttgart · New York.

Examining Internet Usage Demographic Differences and the Relationship between Internet Usage and Business Outcomes in Sierra Leone

ERIC Educational Resources Information Center

Kamara, Mohamed K.

2013-01-01

This study utilized the unified theory of acceptance and use of technology (UTAUT) to determine Internet users' perceptions and behavioral intentions to accept Wi-Fi technology deployment in Sierra Leone. The study sought to investigate (a) the Internet usage rates before and after Wi-Fi adaption in Freetown; (b) differences in Internet usage…

Bayesian approach to the analysis of neutron Brillouin scattering data on liquid metals

NASA Astrophysics Data System (ADS)

De Francesco, A.; Guarini, E.; Bafile, U.; Formisano, F.; Scaccia, L.

2016-08-01

When the dynamics of liquids and disordered systems at mesoscopic level is investigated by means of inelastic scattering (e.g., neutron or x ray), spectra are often characterized by a poor definition of the excitation lines and spectroscopic features in general and one important issue is to establish how many of these lines need to be included in the modeling function and to estimate their parameters. Furthermore, when strongly damped excitations are present, commonly used and widespread fitting algorithms are particularly affected by the choice of initial values of the parameters. An inadequate choice may lead to an inefficient exploration of the parameter space, resulting in the algorithm getting stuck in a local minimum. In this paper, we present a Bayesian approach to the analysis of neutron Brillouin scattering data in which the number of excitation lines is treated as unknown and estimated along with the other model parameters. We propose a joint estimation procedure based on a reversible-jump Markov chain Monte Carlo algorithm, which efficiently explores the parameter space, producing a probabilistic measure to quantify the uncertainty on the number of excitation lines as well as reliable parameter estimates. The method proposed could turn out of great importance in extracting physical information from experimental data, especially when the detection of spectral features is complicated not only because of the properties of the sample, but also because of the limited instrumental resolution and count statistics. The approach is tested on generated data set and then applied to real experimental spectra of neutron Brillouin scattering from a liquid metal, previously analyzed in a more traditional way.

Notes from the Field: Ebola Virus Disease Response Activities During a Mass Displacement Event After Flooding--Freetown, Sierra Leone, September-November, 2015.

PubMed

Ratto, Jeffrey; Ivy, Wade; Purfield, Anne; Bangura, James; Omoko, Anthony; Boateng, Isaac; Duffy, Nadia; Sims, George; Beamer, Bryan; Pi-Sunyer, Teresa; Kamara, Sarian; Conteh, Sulaiman; Redd, John

2016-02-26

Since the start of the Ebola virus disease (Ebola) outbreak in West Africa, Sierra Leone has reported 8,706 confirmed Ebola cases and 3,956 deaths. During September 15-16, 2015, heavy rains flooded the capital, Freetown, resulting in eight deaths, home and property destruction, and thousands of persons in need of assistance. By September 27, approximately 13,000 flood-affected persons registered for flood relief services from the government. On September 17, two stadiums in Freetown were opened to provide shelter and assistance to flood-affected residents; a total of approximately 3,000 persons stayed overnight in both stadiums (Sierra Leone Ministry of Health and Sanitation, personal communication, September 2015). On the same day the stadiums were opened to flood-affected persons, the Ministry of Health and Sanitation (MoHS) and Western Area Ebola Response Center (WAERC) staff members from CDC, the World Health Organization (WHO), and the African Union evaluated the layout, logistics, and services at both stadiums and identified an immediate need to establish Ebola response activities. The patient in the last Ebola case in the Western Area, which includes Freetown, had died 37 days earlier, on August 11; however, transmission elsewhere in Sierra Leone was ongoing, and movement of persons throughout the country was common.

Modeling the 2014 Ebola Virus Epidemic - Agent-Based Simulations, Temporal Analysis and Future Predictions for Liberia and Sierra Leone.

PubMed

Siettos, Constantinos; Anastassopoulou, Cleo; Russo, Lucia; Grigoras, Christos; Mylonakis, Eleftherios

2015-03-09

We developed an agent-based model to investigate the epidemic dynamics of Ebola virus disease (EVD) in Liberia and Sierra Leone from May 27 to December 21, 2014. The dynamics of the agent-based simulator evolve on small-world transmission networks of sizes equal to the population of each country, with adjustable densities to account for the effects of public health intervention policies and individual behavioral responses to the evolving epidemic. Based on time series of the official case counts from the World Health Organization (WHO), we provide estimates for key epidemiological variables by employing the so-called Equation-Free approach. The underlying transmission networks were characterized by rather random structures in the two countries with densities decreasing by ~19% from the early (May 27-early August) to the last period (mid October-December 21). Our estimates for the values of key epidemiological variables, such as the mean time to death, recovery and the case fatality rate, are very close to the ones reported by the WHO Ebola response team during the early period of the epidemic (until September 14) that were calculated based on clinical data. Specifically, regarding the effective reproductive number Re, our analysis suggests that until mid October, Re was above 2.3 in both countries; from mid October to December 21, Re dropped well below unity in Liberia, indicating a saturation of the epidemic, while in Sierra Leone it was around 1.9, indicating an ongoing epidemic. Accordingly, a ten-week projection from December 21 estimated that the epidemic will fade out in Liberia in early March; in contrast, our results flashed a note of caution for Sierra Leone since the cumulative number of cases could reach as high as 18,000, and the number of deaths might exceed 5,000, by early March 2015. However, by processing the reported data of the very last period (December 21, 2014-January 18, 2015), we obtained more optimistic estimates indicative of a remission of

Acoustic dynamics of supercooled indomethacin probed by Brillouin light scattering.

PubMed

De Panfilis, S; Pogna, E A A; Virga, A; Scopigno, T

2014-07-21

Acoustics dynamics of the molecular glass-former indomethacin (IMC) have been investigated by Brillouin light scattering (BLS) at GHz frequencies. Elastic response of the system has been tracked from the melting temperature down to the glass transition through the supercooled liquid. Both the structural arrest and the vibrational dynamics are described by modeling the experimentally determined dynamic structure factor within the framework of the Langevin equation, through a simplified choice of memory function which allows one to determine sound velocity and the acoustic attenuation coefficient as a function of temperature. The density fluctuation spectra in the glassy phase, as probed by BLS, are compared with time-domain results from photoacoustics experiments. The arising scenario is discussed in the context of current literature reporting inelastic X-ray scattering and BLS in platelet geometry. The link between the probed elastic properties and the non-ergodicity factor of the glass phase is finally scrutinized.

Surface Brillouin scattering of opaque solids and thin supported films

PubMed

Comins; Every; Stoddart; Zhang; Crowhurst; Hearne

2000-03-01

Surface Brillouin scattering (SBS) has been used successfully for the study of acoustic excitations in opaque solids and thin supported films, at both ambient and high temperatures. A number of different systems have been investigated recently by SBS including crystalline silicon, amorphous silicon layers produced by ion bombardment and their high temperature recrystallisation, vanadium carbides, and a nickel-based superalloy. The most recent development includes the measurement of a supported gold film at high pressure. The extraction of the elastic constants is successfully accomplished by a combination of the angular dependence of surface wave velocities and the longitudinal wave threshold within the Lamb shoulder. The application of surface Green's function methods successfully reproduces the experimental SBS spectra. The discrepancies often observed between surface wave velocities and by ultrasonics measurements have been investigated and a detailed correction procedure for the SBS measurements has been developed.

Simulation of streamflow and water quality in the Leon Creek watershed, Bexar County, Texas, 1997-2004

USGS Publications Warehouse

Ockerman, Darwin J.; Roussel, Meghan C.

2009-01-01

The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers and the San Antonio River Authority, configured, calibrated, and tested a Hydrological Simulation Program ? FORTRAN watershed model for the approximately 238-square-mile Leon Creek watershed in Bexar County, Texas, and used the model to simulate streamflow and water quality (focusing on loads and yields of selected constituents). Streamflow in the model was calibrated and tested with available data from five U.S. Geological Survey streamflow-gaging stations for 1997-2004. Simulated streamflow volumes closely matched measured streamflow volumes at all streamflow-gaging stations. Total simulated streamflow volumes were within 10 percent of measured values. Streamflow volumes are greatly influenced by large storms. Two months that included major floods accounted for about 50 percent of all the streamflow measured at the most downstream gaging station during 1997-2004. Water-quality properties and constituents (water temperature, dissolved oxygen, suspended sediment, dissolved ammonia nitrogen, dissolved nitrate nitrogen, and dissolved and total lead and zinc) in the model were calibrated using available data from 13 sites in and near the Leon Creek watershed for varying periods of record during 1992-2005. Average simulated daily mean water temperature and dissolved oxygen at the most downstream gaging station during 1997-2000 were within 1 percent of average measured daily mean water temperature and dissolved oxygen. Simulated suspended-sediment load at the most downstream gaging station during 2001-04 (excluding July 2002 because of major storms) was 77,700 tons compared with 74,600 tons estimated from a streamflow-load regression relation (coefficient of determination = .869). Simulated concentrations of dissolved ammonia nitrogen and dissolved nitrate nitrogen closely matched measured concentrations after calibration. At the most downstream gaging station, average simulated monthly

Maternal health, war, and religious tradition: authoritative knowledge in Pujehun District, Sierra Leone.

PubMed

Jambai, A; MacCormack, C

1996-06-01

In Sierra Leone constraints to ideal maternal health require a primary health care approach that includes collaboration with traditional midwives. They are authoritative figures embedded within local political structures and a powerful women's religion. The local causes of maternal risk are described, including civil war and refugee camp life. Traditional midwives provide vital services in the camp, are respected for their social status, and learn additional skills. Biomedical and traditional systems of authoritative knowledge, based on different kinds of legitimacy to heal, are in a complementary relationship.

Housing equity for health equity: a rights-based approach to the control of Lassa fever in post-war Sierra Leone.

PubMed

Kelly, J Daniel; Barrie, M Bailor; Ross, Rachel A; Temple, Brian A; Moses, Lina M; Bausch, Daniel G

2013-01-02

Poor quality housing is an infringement on the rights of all humans to a standard of living adequate for health. Among the many vulnerabilities of those without adequate shelter is the risk of disease spread by rodents and other pests. One such disease is Lassa fever, an acute and sometimes severe viral hemorrhagic illness endemic in West Africa. Lassa virus is maintained in the rodent Mastomys natalensis, commonly known as the "multimammate rat," which frequently invades the domestic environment, putting humans at risk of Lassa fever. The highest reported incidence of Lassa fever in the world is consistently in the Kenema District of Sierra Leone, a region that was at the center of Sierra Leone's civil war in which tens of thousands of lives were lost and hundreds of thousands of dwellings destroyed. Despite the end of the war in 2002, most of Kenema's population still lives in inadequate housing that puts them at risk of rodent invasion and Lassa fever. Furthermore, despite years of health education and village hygiene campaigns, the incidence of Lassa fever in Kenema District appears to be increasing. We focus on Lassa fever as a matter of human rights, proposing a strategy to improve housing quality, and discuss how housing equity has the potential to improve health equity and ultimately economic productivity in Sierra Leone. The manuscript is designed to spur discussion and action towards provision of housing and prevention of disease in one of the world's most vulnerable populations.

Utilisation des fibres optiques dans un interférométre stellalre: demonstration en laboratoire des possibilités d'imagerie, étude et conception de lignes à retard métrique

NASA Astrophysics Data System (ADS)

Delage, L.; Simohamed, L. M.; Reynaud, F.

2018-04-01

This paper, "Utilisation des fibres optiques dans un interférométre stellalre: demonstration en laboratoire des possibilités d'imagerie, étude et conception de lignes à retard métrique," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Population mobility reductions associated with travel restrictions during the Ebola epidemic in Sierra Leone: use of mobile phone data.

PubMed

Peak, Corey M; Wesolowski, Amy; Zu Erbach-Schoenberg, Elisabeth; Tatem, Andrew J; Wetter, Erik; Lu, Xin; Power, Daniel; Weidman-Grunewald, Elaine; Ramos, Sergio; Moritz, Simon; Buckee, Caroline O; Bengtsson, Linus

2018-06-26

Travel restrictions were implementeded on an unprecedented scale in 2015 in Sierra Leone to contain and eliminate Ebola virus disease. However, the impact of epidemic travel restrictions on mobility itself remains difficult to measure with traditional methods. New 'big data' approaches using mobile phone data can provide, in near real-time, the type of information needed to guide and evaluate control measures. We analysed anonymous mobile phone call detail records (CDRs) from a leading operator in Sierra Leone between 20 March and 1 July in 2015. We used an anomaly detection algorithm to assess changes in travel during a national 'stay at home' lockdown from 27 to 29 March. To measure the magnitude of these changes and to assess effect modification by region and historical Ebola burden, we performed a time series analysis and a crossover analysis. Routinely collected mobile phone data revealed a dramatic reduction in human mobility during a 3-day lockdown in Sierra Leone. The number of individuals relocating between chiefdoms decreased by 31% within 15 km, by 46% for 15-30 km and by 76% for distances greater than 30 km. This effect was highly heterogeneous in space, with higher impact in regions with higher Ebola incidence. Travel quickly returned to normal patterns after the restrictions were lifted. The effects of travel restrictions on mobility can be large, targeted and measurable in near real-time. With appropriate anonymization protocols, mobile phone data should play a central role in guiding and monitoring interventions for epidemic containment.

Temperature and molecular-weight dependences of acoustic behaviors of polystyrene studied using Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Oh, Soo Han; Lee, Byoung Wan; Ko, Jae-Hyeon; Lee, Hyeonju; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

2017-04-01

The acoustic properties of three polystyrene polymers with different molecular weights were investigated as a function of temperature by using Brillouin light scattering. The longitudinal sound velocity showed a change in the slope, which depended on the molecular weight, at the glass transition temperature. The absorption coefficient exhibited a maximum above the glass transition temperature, and the maximum temperature became higher as the molecular weight was increased. Comparison with previous acoustic studies on polystyrene indicate that a substantial frequency dispersion caused by strong coupling between the longitudinal acoustic waves and the segmental motions exists in the high-temperature range.

Factors Underlying Ebola Virus Infection Among Health Workers, Kenema, Sierra Leone, 2014-2015.

PubMed

Senga, Mikiko; Pringle, Kimberly; Ramsay, Andrew; Brett-Major, David M; Fowler, Robert A; French, Issa; Vandi, Mohamed; Sellu, Josephine; Pratt, Christian; Saidu, Josephine; Shindo, Nahoko; Bausch, Daniel G

2016-08-15

Ebola virus disease (EVD) in health workers (HWs) has been a major challenge during the 2014-2015 outbreak. We examined factors associated with Ebola virus exposure and mortality in HWs in Kenema District, Sierra Leone. We analyzed data from the Sierra Leone National Viral Hemorrhagic Fever Database, contact tracing records, Kenema Government Hospital (KGH) staff and Ebola Treatment Unit (ETU) rosters, and burial logs. From May 2014 through January 2015, 600 cases of EVD originated in Kenema District, including 92 (15%) HWs, 66 (72%) of whom worked at KGH. Among KGH medical staff and international volunteers, 18 of 62 (29%) who worked in the ETU developed EVD, compared with 48 of 83 (58%) who worked elsewhere in the hospital. Thirteen percent of HWs with EVD reported contact with EVD patients, while 27% reported contact with other infected HWs. The number of HW EVD cases at KGH declined roughly 1 month after implementation of a new triage system at KGH and the opening of a second ETU within the district. The case fatality ratio for HWs and non-HWs with EVD was 69% and 74%, respectively. The cluster of HW EVD cases in Kenema District is one of the largest ever reported. Most HWs with EVD had potential virus exposure both inside and outside of hospitals. Prevention measures for HWs must address a spectrum of infection risks in both formal and informal care settings as well as in the community. © 2016 World Health Organization; licensee Oxford Journals.

Training peers to treat Ebola centre workers with anxiety and depression in Sierra Leone.

PubMed

Waterman, Samantha; Hunter, Elaine Catherine Margaret; Cole, Charles L; Evans, Lauren Jayne; Greenberg, Neil; Rubin, G James; Beck, Alison

2018-03-01

Following the 2014 Ebola virus disease (EVD) outbreak in West Africa, the UK Department for International Development funded South London and Maudsley National Health Service (NHS) to develop a psychological intervention that ex-Ebola Treatment Centre (ETC) staff could be trained to deliver to their peers to improve mental health in Sierra Leone. The two key aims were to assess the feasibility of training a national team to deliver a cognitive behavioural therapy (CBT)-based group intervention, and to evaluate the effectiveness of the overall intervention within this population. UK clinicians travelled to Sierra Leone to train a small team of ex-ETC staff in a three-phased CBT-based intervention. Standardised clinical measures, as well as bespoke measures, were applied with participants through the intervention to assess changes in mental health symptomology, and the effectiveness of the intervention. The results found improvements across all factors of mental health in the bespoke measure from phase 1 to phase 3. Additionally, the majority of standardised clinical measures showed improvements between phase 2 and the start of phase 3, and pre- and post-phase 3. Overall, the findings suggest that it is possible to train staff from ETCs to deliver effective CBT interventions to peers. The implications of these results are discussed, including suggestions for future research and clinical intervention implementation within this population. The limitations of this research are also addressed.

Review: Leon N. Cooper's Science and Human Experience: Values, Culture, and the Mind.

PubMed

Lynch, Gary S

2015-01-01

Why are we reviewing a book written by someone who shared in the 1972 Nobel Prize in Physics for work on superconductivity? Because shortly after winning the prize, Leon N. Cooper transitioned into brain research-specifically, the biological basis of memory. He became director of the Brown University Institute for Brain and Neural Systems, whose interdisciplinary program allowed him to integrate research on the brain, physics, and even philosophy. His new book tackles a diverse spectrum of topics and questions, including these: Does science have limits? Where does order come from? Can we understand consciousness?

Thomson-Scattering Study of the Subharmonic Decay of Ion-Acoustic Waves Driven by the Brillouin Instability

NASA Astrophysics Data System (ADS)

Bandulet, H. C.; Labaune, C.; Lewis, K.; Depierreux, S.

2004-07-01

Thomson scattering (TS) has been used to investigate the two-ion decay instability of ion acoustic waves generated by stimulated Brillouin scattering in an underdense CH plasma. Two complementary TS diagnostics, spectrally and spatially resolved, demonstrate the occurrence of the subharmonic decay of the primary ion acoustic wave into two secondary waves. The study of the laser intensity dependence shows that the secondary ion acoustic waves are correlated with the SBS reflectivity saturation, at a level of a few percent.

Advances of a Brillouin Scattering Lidar System for the Detection of Temperature Profiles in the Ocean: Laboratory Measurements and Field Test

NASA Astrophysics Data System (ADS)

Walther, T.; Rupp, D.; Friman, S.; Trees, C.; Fournier, G.

2016-02-01

Recently we have demonstrated the feasibility of remotely measuring temperature profiles in water under a laboratory environment employing our real-time Brillouin Scattering LIDAR (BSL) system. The working principle is based on the frequency and time resolved detection of the backscattered spontaneous Brillouin signal of a short light pulse fired into the ocean. The light source consists of a frequency-doubled fiber-amplified External Cavity Diode Laser (ECDL) providing high-energy, Fourier transform-limited laser pulses in the green spectral range. The Brillouin shift is detected with high accuracy (low uncertainty) by employing an edge filter based on an Excited State Faraday Anomalous Dispersion Optical Filter (ESFADOF). Time-resolution allows for the depth resolution and the frequency resolved shift is proportional to the speed of sound. Thus, the temperature profile can be extracted from the measurements. In our laboratory setup we were able to resolve water temperatures with a mean accuracy of up to 0.07 oC and a spatial resolution of 1 m depending on the amount of averaging. In order to prepare the system for a first field test under realistic conditions on the coast of the Mediterranean at CMRE in La Spezia, almost all of the components have been upgraded. This first test is planned for November 2015. We will present the above mentioned measurements, details about the upgrades and report on our experiences during this maritime field test.Ultimately, the plan is to operate the system from a mobile platform, e.g., a helicopter or vessel, in order to precisely determine the temperature of the surface mixed layer of the ocean with high spatial resolution.

Potential Exposure to Ebola Virus from Body Fluids due to Ambulance Compartment Permeability in Sierra Leone.

PubMed

Casey, Megan L; Nguyen, Duong T; Idriss, Barrie; Bennett, Sarah; Dunn, Angela; Martin, Stephen

2015-12-01

Prehospital care, including patient transport, is integral in the patient care process during the Ebola response. Transporting ill persons from the community to Ebola care facilities can stop community spread. Vehicles used for patient transport in infectious disease outbreaks should be evaluated for adequate infection prevention and control. An ambulance driver in Sierra Leone attributed his Ebola infection to exposure to body fluids that leaked from the patient compartment to the driver cabin of the ambulance. A convenience sample of 14 vehicles used to transport patients with suspected or confirmed Ebola in Sierra Leone were assessed. The walls separating the patient compartment and driver cabin in these vehicles were evaluated for structural integrity and potential pathways for body fluid leakage. Ambulance drivers and other staff were asked to describe their cleaning and decontamination practices. Ambulance construction and design standards from the National Fire Protection Association, US General Services Administration, and European Committee on Standardization (CEN) were reviewed. Many vehicles used by ambulance staff in Sierra Leone were not traditional ambulances, but were pick-up trucks or sport-utility vehicles that had been assembled or modified for patient transport. The wall separating the patient compartment and driver cabin in many vehicles did not have a waterproof seal around the edges. Staff responsible for cleaning and disinfection did not thoroughly clean bulk body fluids with disposable towels before disinfection of the patient compartment. Pressure from chlorine sprayers used in the decontamination process may have pushed body fluids from the patient compartment into the driver cabin through gaps around the wall. Ambulance design standards do not require a waterproof seal between the patient compartment and driver cabin. Sealing the wall by tightening or replacing existing bolts is recommended, followed by caulking of all seams with a

Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis and preventive chemotherapy strategies in Sierra Leone.

PubMed

Koroma, Joseph B; Peterson, Jen; Gbakima, Aiah A; Nylander, Francis E; Sahr, Foday; Soares Magalhães, Ricardo J; Zhang, Yaobi; Hodges, Mary H

2010-11-23

A national baseline mapping of schistosomiasis and soil-transmitted helminthiasis (STH) was performed in Sierra Leone. The aim was to provide necessary tools for the Ministry of Health and Sanitation to plan the intervention strategies in the national integrated control program on neglected tropical diseases according to the World Health Organization (WHO) guidelines for preventative chemotherapy (PCT) and for future monitoring and evaluation. 53 primary schools were randomly selected through a two-staged random sampling throughout the country. Approximately one hundred children aged 5-16 years of age were systematically selected from each school and their stool samples examined in a field laboratory. A total of 5,651 samples were examined. Data were analyzed with multivariable logistic regression models using model-based geostatistics. Spatial analysis predicted that S. mansoni infection was positively associated with population density and elevation and that there was a large cluster of high risk of S. mansoni infection (prevalence >70%) in the north and most of the eastern areas of the country, in line with the observed prevalence in Kono (63.8-78.3%), Koinadugu (21.6-82.1%), Kailahun (43.5-52.6%), Kenema (6.1-68.9%) and Tonkolili (0-57.3%). Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country. Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s. Results justify PCT for schistosomiasis for school age children and at-risk adults every year in high-risk communities in five districts and every two years in moderate-risk communities in one more district. The high prevalence of STH, particularly hookworm, coupled with widespread anemia according to a national report in Sierra Leone, suggests

A Comprehensive Vocational Education Program for Career Development in Leon County. Final Report. Volume 1. Program Performance Report.

ERIC Educational Resources Information Center

Leon County Schools, Tallahassee, FL.

The document presents an account of project activities that evolved around the development and implementation of career education in Leon County School District, Florida. The purpose of the project was to begin effecting needed educational changes at the K-14 level by developing a comprehensive career education program designed to increase student…

Robust, Brillouin Active Embedded Fiber-Is-The-Sensor System in Smart Composite Structures

NASA Technical Reports Server (NTRS)

Yu, Chung

1996-01-01

Extensive review of our proposed sensing scheme, based mainly on the forward Guided Acoustic Wave Brillouin Scattering (GAWBS) with backward stimulated Brillouin scattering (sBs) as an auxiliary scheme for system fault tolerance has been completed during this project period. This preliminary study is conducted for a number of reasons. The most significant reasons lie in the essential capability of the system to measure temperature and pressure. These two measurands have been proposed to be sensed by sBs in our proposal. Temperature and pressure/strain are important measurands in structural monitoring, so that the effectiveness of sensing by sBs needs to be further examined. It has been pointed out initially that sBs shift will be dependent on temperature and pressure/strain simultaneously. The shift versus temperature or strain is linear. Now, the question is how can these two measurands be separated when sBs is used to sense an environment, in which both temperature and strain are changing simultaneously. Typical sBs shift plotted versus strain and varying temperature is shown in Fig. 1. As is clear, a fiber initially stressed will relax with rising temperature. This is verified by a displacement to the right with rising temperature of the sBs shift vs strain curves in the figure. A way to circumvent this ambiguity is by employing two fibers, one pre-stressed and the other is a free fiber. The latter will measure temperature and subtracting data in the latter fiber from those of the former will give us net strain readings. This is a laborious approach, since it involves the use of two identical fibers, and this is hard to accomplish, especially when many sensors are needed. Additional multiplexing of the data stream for data subtraction becomes a necessity.

Acoustic and relaxation behaviors of polydimethylsiloxane studied by using brillouin and dielectric spectroscopies

NASA Astrophysics Data System (ADS)

Lee, Byoung Wan; Ko, Jae-Hyeon; Park, Jaehoon; Shin, Dong-Myeong; Hwang, Yoon-Hwae

2016-04-01

The temperature dependences of the acoustic properties and the dielectric relaxation times of polydimethylsiloxane were investigated by using high-resolution Brillouin and broadband dielectric spectroscopies. The longitudinal sound velocity showed a large increase upon approaching the glass transition temperature while the acoustic absorption coefficient exhibited a maximum at ~263 K. Comparison of these results with previous ultrasonic data revealed a substantial frequency dispersion of the acoustic properties of this silicone-based elastomer. The relaxation times derived from the acoustic absorption peaks were consistent with the temperature dependence of the dielectric relaxation time of the structural a process, indicating a strong coupling between the acoustic waves and the segmental motions of the main chains.

Adolescent fertility management: the Sierra Leone experience.

PubMed

Lamin, M M; Singleton, A

1982-01-01

Because of growing concerns for the problems of adolescent fertility, a training program in Adolescent Fertility Management was conducted in Sierra Leone in 1981. The program was designed to actuate the interdisciplinary energies necessary for exploring the depth of the problem and to develop strategies for possible solutions. 2 program activities were conducted: a Former Participant Conference, which resulted in the development of a draft of a country-wide program; and a 2-week training workshop. In order to create public awareness, the participants presented an original drama, a synopsis of which is provided. Solutions to the problems of adolescent fertility must address not only the availability and use of contraceptives, but also a reorientation of the attitudes of parents on sex education. The practice of expelling pregnant adolescents from educational institutions only serves to compound the problems. A list of the topics covered during the workshops is provided, as are a summary of the conclusions and subsequent recommendations. Participants voted to form a national organization whose main objective is the reduction of teenage pregnancy by at least 12% within a 12 month period through the creation of a national awareness campaign.

Survivors' perceptions of public health messages during an Ebola crisis in Liberia and Sierra Leone: An exploratory study.

PubMed

Schwerdtle, Patricia; De Clerck, Veronique; Plummer, Virginia

2017-12-01

The outbreak of Ebola virus disease in Guinea, Liberia, and Sierra Leone was the largest epidemic of Ebola ever recorded. The healthcare workforce was diminished and exhausted as the region emerged from civil war. Few qualitative, descriptive studies have been conducted to date that concentrate on the voices of Ebola survivors and their perceptions of health messages. In this study, we employed an interpretive, qualitative design to explore participant experiences. Twenty five survivors who had recovered from Ebola were recruited from three villages in Liberia and Sierra Leone in August 2015. Data were collected using semistructured interviews. Data analysis revealed four themes: (i) degrees of mistrust; (ii) messages conflicting with life and culture; (iii) seeing is believing; and (iv) recovery inspires hope. The findings were explored in the context of the relevant literature. The themes highlight the need to develop culturally-appropriate messages, underpinned by a sound understanding of the community and a willingness to work with the culture and trusted leaders. © 2017 John Wiley & Sons Australia, Ltd.

[Remarks on Leon Popielski's manuscript of his review of January Zubrzycki's qualifying thesis for professorship dating from 1915].

PubMed

Heimrath, T

1994-01-01

A review written by professor Leon Popielski from Lvov of the qualifying thesis for professorship of January Zubrzycki from Cracow is presented. The manuscript has been kept by professor Popielski's family. Zubrzycki finished his medical studies in Cracow in 1909. While writing his qualifying thesis entitled Placental Albumin Derivatives and their Toxic Properties in 1915 he was an assistant of Aleksander Rosner in the department of maternity and gynaecology of Jagiellonian University. In 1931 as a professor he became the head of the clinic and following the Second World War he was a professor at several faculties of medicine in Poland. He was an outstanding gynaecological surgeon, an author of a five volume atlas of gynaecological surgery. Professor Leon Popielski studied in S. Petersburg. He specialized in physiology. Since 1904 he was the head of the Chair of Pharmacologoy and Pharmacognosy at the Universitiy of Lvov. Popielski's intrest in Zubrzycki's work ensued his research on albumin metabolite effect. His appreciation of the work is expressed by the phrase "I read it with satisfaction". The review was written in 1919, belated by the war.

Self-starting picosecond optical pulse source using stimulated Brillouin scattering in an optical fiber.

PubMed

Tang, W W; Shu, C

2005-02-21

We demonstrate a regeneratively mode-locked optical pulse source at about 10 GHz using an optoelectronic oscillator constructed with an electro-absorption modulator integrated distributed feedback laser diode. The 10 GHz RF component is derived from the interaction between the pump wave and the backscattered, frequency-downshifted Stokes wave resulted from stimulated Brillouin scattering in an optical fiber. The component serves as a modulation source for the 1556 nm laser diode without the need for any electrical or optical RF filter to perform the frequency extraction. Dispersion-compensated fiber, dispersion-shifted fiber, and standard single-mode fiber have been used respectively to generate optical pulses at variable repetition rates.

Light scattering by a nematic liquid crystal droplet: Wentzel–Kramers–Brillouin approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loiko, V. A., E-mail: loiko@dragon.bas-net.by; Konkolovich, A. V.; Miskevich, A. A.

2016-01-15

Light scattering by an optically anisotropic liquid crystal (LC) droplet of a nematic in an isotropic polymer matrix is considered in the Wentzel–Kramers–Brillouin (WKB) approximation. General relations are obtained for elements of the amplitude matrix of light scattering by a droplet of arbitrary shape and for the structure of the director field. Analytic expressions for the amplitude matrices are derived for spherical LC droplets with a uniformly oriented structure of local optical axes for strictly forward and strictly backward scattering. The efficiency factors of extinction and backward scattering for a spherical nonabsorbing LC droplet depending on the LC optical anisotropy,more » refractive index of the polymer, illumination conditions, and orientation of the optical axis of the droplet are analyzed. Verification of the obtained solutions has been performed.« less

Stimulated Brillouin scattering continuous wave phase conjugation in step-index fiber optics.

PubMed

Massey, Steven M; Spring, Justin B; Russell, Timothy H

2008-07-21

Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length. A phase conjugate fidelity over 80% was measured from SBS in a 40 m fiber using a pinhole technique. Fidelity decreases with fiber length, and a fiber with a numerical aperture (NA) of 0.06 was found to generate good phase conjugation fidelity over longer lengths than a fiber with 0.13 NA. Modeling and experiment support previous work showing the maximum interaction length which yields a high fidelity phase conjugate beam is inversely proportional to the fiber NA(2), but find that fidelity remains high over much longer fiber lengths than previous models calculated. Conditions for SBS beam cleanup in step-index fibers are discussed.

[Effects of reforestation on tree pollen sensitization in inhabitants of Nuevo Leon, Mexico].

PubMed

Palma-Gómez, Samuel; González-Díaz, Sandra Nora; Arias-Cruz, Alfredo; Macías-Weinmann, Alejandra; Amaro-Vivian, Laura Elizabeth; Pérez-Vanzzini, Rafael; Gutiérrez-Mujica, José Julio; Yong-Rodríguez, Adrián

2014-01-01

Climate change has implications for health, ecology and society. Urban green areas are a key element in the planning of cities, promoting citizen interaction with the environment, as well as health. Lack of planning and design of these areas as well as the selection of ornamental trees can be a trigger of pollen allergy in the surrounding population. Reforestation is among the programs implemented by the government that have an impact on allergy. Environmental reforestation programs do not take into account the allergenic potential of some species. In the last 4 years, the government of Nuevo Leon, Mexico, has planted nearly 18,000 Quercus species trees, in addition to an unknown number of Fraxinus species trees that are listed as tree species with high pollen production. To identify changes in tree pollen sensitization, based on environmental reforestation programs. A retrospective and descriptive study was done in which positive skin prick tests to pollen from trees in the interval of 2010-2014 were analyzed, correlating between tree species used for reforestation and increased sensitivity to the former. A statistically significant increase in pollen sensitization to species with which Nuevo Leon was reforested was found, along with a decrease in sensitization to the species that were not reforested. Reforestation contributes to some extent to the change in the pattern of positive skin tests and may result in more frequent exacerbations of respiratory diseases. It is an activity that should always be regulated and assisted by experts in the according field.

Community-based birth waiting homes in Northern Sierra Leone: Factors influencing women's use.

PubMed

Kyokan, Michiko; Whitney-Long, Melissa; Kuteh, Mabel; Raven, Joanna

2016-08-01

to explore the factors influencing women's use of birth waiting homes in the Northern Bombali district, Sierra Leone. this was a descriptive exploratory study using qualitative research methodology, which included in depth interviews, key informant interviews, focus group discussions, document review and observations. two chiefdoms in the Northern Bombali district, Sierra Leone. eight interviews were conducted with women who had delivered in the past one year and used birth waiting homes; eight key informant interviews with a project manager, birth waiting homes hosts, and community members; thirteen women who delivered in the past year without using birth waiting homes (four interviews and two focus group discussions). there are several factors influencing the use of birth waiting homes (BWHs) including: past experience of childbirth, promotion of the birth waiting homes by traditional birth attendance, distance and costs of transport to the homes, child care and other family commitments, family's views of the importance of the homes, the costs of food during women's stay, and information given to women and families about when and how to use the homes. some barriers, especially those related to family commitments and costs of food, are challenging to solve. In order to make a BWH a user-friendly and viable option, it may be necessary to adjust ways in which BWHs are used. Good linkage with the health system is strength of the programme. However, further strengthening of community participation in monitoring and managing the BWHs is needed for the long term success and sustainability of the BWHs. Copyright © 2016 Elsevier Ltd. All rights reserved.

An Examination of Primary School Attendance and Completion among Secondary School Age Adolescents in Post-Conflict Sierra Leone

ERIC Educational Resources Information Center

Moyi, Peter

2013-01-01

Sierra Leone was ravaged by a civil war between 1991 and 2002. Since the end of the war, it has witnessed an unprecedented increase in school enrollments. Although school enrollment has increased, the number of school age children who are out of school remains high. The focus of international agencies is on children of primary school age, yet a…

Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves.

PubMed

Antman, Yair; Levanon, Nadav; Zadok, Avi

2012-12-15

A method for long variable all-optical delay is proposed and simulated, based on reflections from localized and stationary dynamic Brillouin gratings (DBGs). Inspired by radar methods, the DBGs are inscribed by two pumps that are comodulated by perfect Golomb codes, which reduce the off-peak reflectivity. Compared with random bit sequence coding, Golomb codes improve the optical signal-to-noise ratio (OSNR) of delayed waveforms by an order of magnitude. Simulations suggest a delay of 5  Gb/s data by 9 ns, or 45 bit durations, with an OSNR of 13 dB.

Surface-coupling of Cerenkov radiation from a modified metallic metamaterial slab via Brillouin-band folding.

PubMed

Bera, Anirban; Barik, Ranjan Kumar; Sattorov, Matlabjon; Kwon, Ohjoon; Min, Sun-Hong; Baek, In-Keun; Kim, Seontae; So, Jin-Kyu; Park, Gun-Sik

2014-02-10

Metallic metamaterials with positive dielectric responses are promising as an alternative to dielectrics for the generation of Cerenkov radiation [J.-K. So et al., Appl. Phys. Lett. 97(15), 151107 (2010)]. We propose here by theoretical analysis a mechanism to couple out Cerenkov radiation from the slab surfaces in the transverse direction. The proposed method based on Brillouin-zone folding is to periodically modify the thickness of the metamaterial slab in the axial direction. Moreover, the intensity of the surface-coupled radiation by this mechanism shows an order-of-magnitude enhancement compared to that of ordinary Smith-Purcell radiation.

Health knowledge and health practices in Makeni, Sierra Leone: a community-based household survey.

PubMed

Abdelmalak, Mena J; Ahmed, Bilaal S; Mehta, Khanjan

2016-05-01

We characterize health knowledge and practices in urban and rural Makeni, Sierra Leone, drawing comparisons between areas served by community health workers (CHWs) with those that are not. We also inquire about causes of infant and maternal mortality and how they are understood in the local context. Our objective was to provide a baseline understanding of health knowledge and practices in Makeni during the implementation of a CHW program. We conducted 100 household interviews in Makeni City and rural villages in the surrounding area. We compared data between urban and rural areas to identify differences in health knowledge and practices. Our sample size covered 855 individuals. Insecticide treated bednet ownership was lower in urban settings compared to rural populations (58% vs 94%; p<.001). With regards to maternal mortality, most respondents indicated 'no clinic' (lack of clinical care or skipped antenatal care visits) as the primary cause (n=35), followed by bleeding (n=17), 'lack of blood' (anemia) (n=11) and 'will of God' (n=11). This initial survey of health knowledge and practices in rural and urban Makeni, Sierra Leone, highlights some simple opportunities for community health promotion, health education programming and behavioral interventions. Findings will inform future iterations of a CHW training module for community health education. © The Author 2015. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Study of the Wall Paintings of the Cenador Del Leon in the Real Alcazar of Seville

NASA Astrophysics Data System (ADS)

Robador, Maria Dolores; Mancera, Inmaculada; Perez-Maqueda, Rafael; Albardonedo, Antonio

2017-10-01

The paintings on the walls of the Cenador del Leon located in the gardens of the Real Alcazar in Seville next to the Pabellon de Carlos V in the Jardin Ingles area have been studied. The components of the wall paintings cross-sections, which were prepared using small samples taken from the walls of Cenador del Leon, were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. The cross-sections of the collected samples indicated that the paint layer is well adhered to the preparation layer without any discontinuity, and only one carbonation layer exists at the top of the sequence of layers. These data suggest that the paint was applied on a fresco surface, and therefore, the adopted technique was fresco. Based on the different elements detected by EDX analysis of the cross-sections, the detected pigments included iron oxides accompanied by clay minerals (or earths) in the red pink, golden yellow and yellow colours, blue smelt for the blue colour and basic copper chloride (atacamite) for the green colour. In one sample, the particles were composed of Ba and S from barium sulphate and Ti and O from rutile titanium oxide due to a modern pigment.

Situation Report--Australia, Burundi, Cambodia, Mexico, Montserrat, Nicaragua, Papua & New Guinea, Republic of Vietnam, Sabah, Sarawak, Sierra Leone, Tahiti, Tonga.

ERIC Educational Resources Information Center

International Planned Parenthood Federation, London (England).

Data relating to population and family planning in fourteen foreign countries are presented in these situation reports. Countries included are Australia, Burundi, Cambodia, Mexico, Montserrat, Nicaragua, Papua and New Guines, Republic of Vietnam, Sabah, Sarawak, Sierra Leone, Tahiti (French Polynesia), and Tonga. Information is provided under two…

Leon Van Speybroeck Wins Astrophysics Bruno Rossi Prize

NASA Technical Reports Server (NTRS)

2002-01-01

Leon Van Speybroeck of the Harvard-Smithsonian Center for Astrophysics in Cambridge Massachusetts was awarded the 2002 Bruno Rossi Prize of the High-Energy Astrophysics Division of the American Astronomy Society. The Rossi Prize is an arnual recognition of significant contributions in high-energy astrophysics in honor of the Massachusetts Institute of Technology's late Professor Bruno Rossi, an authority on cosmic ray physics and a pioneer in the field of x-ray astronomy. Van Speybroeck, who led the effort to design and make the x-ray mirrors for NASA's premier Chandra X-Ray Observatory, was recognized for a career of stellar achievements in designing precision x-ray optics. As Telescope Scientist for Chandra, he has worked for more than 20 years with a team that includes scientists and engineers from the Harvard-Smithsonian, NASA's Marshall Space Flight Center, TRW, Inc., Huhes-Danbury (now B.F. Goodrich Aerospace), Optical Coating Laboratories, Inc., and Eastman-Kodak on all aspects of the x-ray mirror assembly that is the heart of the observatory.

Traumatic injuries in developing countries: report from a nationwide cross-sectional survey of Sierra Leone.

PubMed

Stewart, Kerry-Ann A; Groen, Reinou S; Kamara, Thaim B; Farahzad, Mina M; Samai, Mohamed; Cassidy, Laura D; Kushner, Adam L; Wren, Sherry M

2013-05-01

To use a nationwide household survey tool to provide an estimate of injury prevalence, mechanisms of traumatic injuries, and number of injury-related deaths in a low-income country. A randomized, cross-sectional nationwide survey using the Surgeons OverSeas Assessment of Surgical Need tool was conducted in 2012. Sierra Leone, Africa. Three thousand seven hundred fifty randomly selected participants throughout Sierra Leone. Mechanisms of injury based on age, sex, anatomic location, cause, and sociodemographic factors as well as mechanisms of injury-related deaths in the previous year were the primary outcome measures. Data were collected and analyzed from 1843 households and 3645 respondents (98% response rate). Four hundred fifty-two respondents (12%) reported at least 1 traumatic injury in the preceding year. Falls were the most common cause of nonfatal injuries (40%). The extremities were the most common injury site regardless of age or sex. Traffic injuries were the leading cause of injury-related deaths (32% of fatal injuries). This study provides baseline data on the mechanisms of traumatic injuries as well as the sociodemographic factors affecting injury prevalence in one of the world's poorest nations. It is anticipated that these data will provide an impetus for further studies to determine injury severity, associated disability, and barriers to accessing care in these resource-poor areas.

Beyond the random phase approximation: Stimulated Brillouin backscatter for finite laser coherence times

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korotkevich, Alexander O.; Lushnikov, Pavel M., E-mail: plushnik@math.unm.edu; Landau Institute for Theoretical Physics, 2 Kosygin Str., Moscow 119334

2015-01-15

We developed a linear theory of backward stimulated Brillouin scatter (BSBS) of a spatially and temporally random laser beam relevant for laser fusion. Our analysis reveals a new collective regime of BSBS (CBSBS). Its intensity threshold is controlled by diffraction, once cT{sub c} exceeds a laser speckle length, with T{sub c} the laser coherence time. The BSBS spatial gain rate is approximately the sum of that due to CBSBS, and a part which is independent of diffraction and varies linearly with T{sub c}. The CBSBS spatial gain rate may be reduced significantly by the temporal bandwidth of KrF-based laser systemsmore » compared to the bandwidth currently available to temporally smoothed glass-based laser systems.« less

Novel Retinal Lesion in Ebola Survivors, Sierra Leone, 2016.

PubMed

Steptoe, Paul J; Scott, Janet T; Baxter, Julia M; Parkes, Craig K; Dwivedi, Rahul; Czanner, Gabriela; Vandy, Matthew J; Momorie, Fayiah; Fornah, Alimamy D; Komba, Patrick; Richards, Jade; Sahr, Foday; Beare, Nicholas A V; Semple, Malcolm G

2017-07-01

We conducted a case-control study in Freetown, Sierra Leone, to investigate ocular signs in Ebola virus disease (EVD) survivors. A total of 82 EVD survivors with ocular symptoms and 105 controls from asymptomatic civilian and military personnel and symptomatic eye clinic attendees underwent ophthalmic examination, including widefield retinal imaging. Snellen visual acuity was <6/7.5 in 75.6% (97.5% CI 63%-85.7%) of EVD survivors and 75.5% (97.5% CI 59.1%-87.9%) of controls. Unilateral white cataracts were present in 7.4% (97.5% CI 2.4%-16.7%) of EVD survivors and no controls. Aqueous humor from 2 EVD survivors with cataract but no anterior chamber inflammation were PCR-negative for Zaire Ebola virus, permitting cataract surgery. A novel retinal lesion following the anatomic distribution of the optic nerve axons occurred in 14.6% (97.5% CI 7.1%-25.6%) of EVD survivors and no controls, suggesting neuronal transmission as a route of ocular entry.

Development of a Pediatric Ebola Predictive Score, Sierra Leone1.

PubMed

Fitzgerald, Felicity; Wing, Kevin; Naveed, Asad; Gbessay, Musa; Ross, J C G; Checchi, Francesco; Youkee, Daniel; Jalloh, Mohamed Boie; Baion, David E; Mustapha, Ayeshatu; Jah, Hawanatu; Lako, Sandra; Oza, Shefali; Boufkhed, Sabah; Feury, Reynold; Bielicki, Julia; Williamson, Elizabeth; Gibb, Diana M; Klein, Nigel; Sahr, Foday; Yeung, Shunmay

2018-02-01

We compared children who were positive for Ebola virus disease (EVD) with those who were negative to derive a pediatric EVD predictor (PEP) score. We collected data on all children <13 years of age admitted to 11 Ebola holding units in Sierra Leone during August 2014-March 2015 and performed multivariable logistic regression. Among 1,054 children, 309 (29%) were EVD positive and 697 (66%) EVD negative, with 48 (5%) missing. Contact history, conjunctivitis, and age were the strongest positive predictors for EVD. The PEP score had an area under receiver operating characteristics curve of 0.80. A PEP score of 7/10 was 92% specific and 44% sensitive; 3/10 was 30% specific, 94% sensitive. The PEP score could correctly classify 79%-90% of children and could be used to facilitate triage into risk categories, depending on the sensitivity or specificity required.

Development of a set of community-informed Ebola messages for Sierra Leone

PubMed Central

de Bruijne, Kars; Jalloh, Alpha M.; Harris, Muriel; Abdullah, Hussainatu; Boye-Thompson, Titus; Sankoh, Osman; Jalloh, Abdul K.; Jalloh-Vos, Heidi

2017-01-01

The West African Ebola epidemic of 2013–2016 was by far the largest outbreak of the disease on record. Sierra Leone suffered nearly half of the 28,646 reported cases. This paper presents a set of culturally contextualized Ebola messages that are based on the findings of qualitative interviews and focus group discussions conducted in 'hotspot' areas of rural Bombali District and urban Freetown in Sierra Leone, between January and March 2015. An iterative approach was taken in the message development process, whereby (i) data from formative research was subjected to thematic analysis to identify areas of community concern about Ebola and the national response; (ii) draft messages to address these concerns were produced; (iii) the messages were field tested; (iv) the messages were refined; and (v) a final set of messages on 14 topics was disseminated to relevant national and international stakeholders. Each message included details of its rationale, audience, dissemination channels, messengers, and associated operational issues that need to be taken into account. While developing the 14 messages, a set of recommendations emerged that could be adopted in future public health emergencies. These included the importance of embedding systematic, iterative qualitative research fully into the message development process; communication of the subsequent messages through a two-way dialogue with communities, using trusted messengers, and not only through a one-way, top-down communication process; provision of good, parallel operational services; and engagement with senior policy makers and managers as well as people in key operational positions to ensure national ownership of the messages, and to maximize the chance of their being utilised. The methodological approach that we used to develop our messages along with our suggested recommendations constitute a set of tools that could be incorporated into international and national public health emergency preparedness and

Effect of pore occupancy on the acoustic properties of zeolitic imidazolate framework (ZIF)-8: A Brillouin spectroscopic study at ambient and low temperatures

NASA Astrophysics Data System (ADS)

Radhakrishnan, Dhanya; Narayana, Chandrabhas

2015-12-01

Brillouin spectroscopy is used to study the effect of pore occupancy on the elastic constants by incorporating various guest molecules into zeolitic imidazolate framework (ZIF)-8. A systematic study on the effect of mass and polarizability of the guest has been carried out by incorporating alcohols of varying chain lengths at room temperature. The interaction between the guest and host affects the elastic properties, lifetimes and guest dynamics inside the pores. The elastic anisotropy was seen to reduce upon incorporation of the guests. We have also studied the temperature dependence of the acoustic modes on gas adsorption to understand the framework flexibility. The Brillouin shift of the acoustic modes increases upon temperature dependent gas adsorption with transverse acoustic modes exhibiting a larger shift. This suggests a hardening of otherwise low shear modulus of ZIF-8. Our findings give insight into the role of guest molecules and temperature in tuning the elastic properties of ZIF-8 which is important for practical applications.

Laser-induced damage of fused silica optics at 355 nm due to backward stimulated Brillouin scattering: experimental and theoretical results.

PubMed

Lamaignère, Laurent; Gaudfrin, Kévin; Donval, Thierry; Natoli, Jeanyves; Sajer, Jean-Michel; Penninckx, Denis; Courchinoux, Roger; Diaz, Romain

2018-04-30

Forward pump pulses with nanosecond duration are able to generate an acoustic wave via electrostriction through a few centimeters of bulk silica. Part of the incident energy is then scattered back on this sound wave, creating a backward Stokes pulse. This phenomenon known as stimulated Brillouin scattering (SBS) might induce first energy-loss, variable change of the temporal waveform depending on the location in the spatial profile making accurate metrology impossible, and moreover it might also initiate front surface damage making the optics unusable. Experiments performed on thick fused silica optics at 355 nm with single longitudinal mode pulses allowed us to detect, observe and quantify these backward pulses. Experimental results are first compared to theoretical calculations in order to strengthen our confidence in metrology. On this basis a phase-modulator has been implemented on the continuous-wave seeders of the lasers leading to pulses with a wide spectrum that suppress SBS and do not exhibit temporal overshoots that also reduce Kerr effects. The developed set-ups are used to check the reduction of the backward stimulated Brillouin scattering and they allow measuring with accuracy the rear surface damage of thick fused silica optics.

Brillouin spectroscopy of fluid inclusions proposed as a paleothermometer for subsurface rocks.

PubMed

El Mekki-Azouzi, Mouna; Tripathi, Chandra Shekhar Pati; Pallares, Gaël; Gardien, Véronique; Caupin, Frédéric

2015-08-28

As widespread, continuous instrumental Earth surface air temperature records are available only for the last hundred fifty years, indirect reconstructions of past temperatures are obtained by analyzing "proxies". Fluid inclusions (FIs) present in virtually all rock minerals including exogenous rocks are routinely used to constrain formation temperature of crystals. The method relies on the presence of a vapour bubble in the FI. However, measurements are sometimes biased by surface tension effects. They are even impossible when the bubble is absent (monophasic FI) for kinetic or thermodynamic reasons. These limitations are common for surface or subsurface rocks. Here we use FIs in hydrothermal or geodic quartz crystals to demonstrate the potential of Brillouin spectroscopy in determining the formation temperature of monophasic FIs without the need for a bubble. Hence, this novel method offers a promising way to overcome the above limitations.

Brillouin spectroscopy of fluid inclusions proposed as a paleothermometer for subsurface rocks

PubMed Central

Mekki-Azouzi, Mouna El; Tripathi, Chandra Shekhar Pati; Pallares, Gaël; Gardien, Véronique; Caupin, Frédéric

2015-01-01

As widespread, continuous instrumental Earth surface air temperature records are available only for the last hundred fifty years, indirect reconstructions of past temperatures are obtained by analyzing “proxies”. Fluid inclusions (FIs) present in virtually all rock minerals including exogenous rocks are routinely used to constrain formation temperature of crystals. The method relies on the presence of a vapour bubble in the FI. However, measurements are sometimes biased by surface tension effects. They are even impossible when the bubble is absent (monophasic FI) for kinetic or thermodynamic reasons. These limitations are common for surface or subsurface rocks. Here we use FIs in hydrothermal or geodic quartz crystals to demonstrate the potential of Brillouin spectroscopy in determining the formation temperature of monophasic FIs without the need for a bubble. Hence, this novel method offers a promising way to overcome the above limitations. PMID:26316328

High-temperature elastic properties of a nickel-based superalloy studied by surface Brillouin scattering

NASA Astrophysics Data System (ADS)

Zhang, X.; Stoddart, P. R.; Comins, J. D.; Every, A. G.

2001-03-01

Surface Brillouin scattering (SBS) has been used to study the thermally induced surface vibrations (phonons) and thereby obtain the elastic properties of the nickel-based superalloy CMSX-4. SBS spectra have been acquired for a range of wavevector directions in the (001) surface in the single-crystal specimen to determine the angular variation of SAW velocities and the nature of the various excitations. Rayleigh and pseudo-surface acoustic waves as well as the details of the Lamb shoulder are studied, and the elastic constants and engineering moduli are determined using different, but self-consistent, methods at ambient and high temperatures. Calculations of the SBS spectra using surface Green function methods are in good agreement with the experimental results.

Estimating the future number of cases in the Ebola epidemic--Liberia and Sierra Leone, 2014-2015.

PubMed

Meltzer, Martin I; Atkins, Charisma Y; Santibanez, Scott; Knust, Barbara; Petersen, Brett W; Ervin, Elizabeth D; Nichol, Stuart T; Damon, Inger K; Washington, Michael L

2014-09-26

The first cases of the current West African epidemic of Ebola virus disease (hereafter referred to as Ebola) were reported on March 22, 2014, with a report of 49 cases in Guinea. By August 31, 2014, a total of 3,685 probable, confirmed, and suspected cases in West Africa had been reported. To aid in planning for additional disease-control efforts, CDC constructed a modeling tool called EbolaResponse to provide estimates of the potential number of future cases. If trends continue without scale-up of effective interventions, by September 30, 2014, Sierra Leone and Liberia will have a total of approximately 8,000 Ebola cases. A potential underreporting correction factor of 2.5 also was calculated. Using this correction factor, the model estimates that approximately 21,000 total cases will have occurred in Liberia and Sierra Leone by September 30, 2014. Reported cases in Liberia are doubling every 15-20 days, and those in Sierra Leone are doubling every 30-40 days. The EbolaResponse modeling tool also was used to estimate how control and prevention interventions can slow and eventually stop the epidemic. In a hypothetical scenario, the epidemic begins to decrease and eventually end if approximately 70% of persons with Ebola are in medical care facilities or Ebola treatment units (ETUs) or, when these settings are at capacity, in a non-ETU setting such that there is a reduced risk for disease transmission (including safe burial when needed). In another hypothetical scenario, every 30-day delay in increasing the percentage of patients in ETUs to 70% was associated with an approximate tripling in the number of daily cases that occur at the peak of the epidemic (however, the epidemic still eventually ends). Officials have developed a plan to rapidly increase ETU capacities and also are developing innovative methods that can be quickly scaled up to isolate patients in non-ETU settings in a way that can help disrupt Ebola transmission in communities. The U.S. government and

Geographical Distribution of Intestinal Schistosomiasis and Soil-Transmitted Helminthiasis and Preventive Chemotherapy Strategies in Sierra Leone

PubMed Central

Koroma, Joseph B.; Peterson, Jen; Gbakima, Aiah A.; Nylander, Francis E.; Sahr, Foday; Soares Magalhães, Ricardo J.; Zhang, Yaobi; Hodges, Mary H.

2010-01-01

Background A national baseline mapping of schistosomiasis and soil-transmitted helminthiasis (STH) was performed in Sierra Leone. The aim was to provide necessary tools for the Ministry of Health and Sanitation to plan the intervention strategies in the national integrated control program on neglected tropical diseases according to the World Health Organization (WHO) guidelines for preventative chemotherapy (PCT) and for future monitoring and evaluation. Methodology/Principal Findings 53 primary schools were randomly selected through a two-staged random sampling throughout the country. Approximately one hundred children aged 5–16 years of age were systematically selected from each school and their stool samples examined in a field laboratory. A total of 5,651 samples were examined. Data were analyzed with multivariable logistic regression models using model-based geostatistics. Spatial analysis predicted that S. mansoni infection was positively associated with population density and elevation and that there was a large cluster of high risk of S. mansoni infection (prevalence >70%) in the north and most of the eastern areas of the country, in line with the observed prevalence in Kono (63.8–78.3%), Koinadugu (21.6–82.1%), Kailahun (43.5–52.6%), Kenema (6.1–68.9%) and Tonkolili (0–57.3%). Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country. Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s. Conclusions/Significance Results justify PCT for schistosomiasis for school age children and at-risk adults every year in high-risk communities in five districts and every two years in moderate-risk communities in one more district. The high prevalence of STH, particularly hookworm, coupled

Impact of five annual rounds of mass drug administration with ivermectin on onchocerciasis in Sierra Leone.

PubMed

Koroma, Joseph B; Sesay, Santigie; Conteh, Abdul; Koudou, Benjamin; Paye, Jusufu; Bah, Mohamed; Sonnie, Mustapha; Hodges, Mary H; Zhang, Yaobi; Bockarie, Moses J

2018-04-06

Onchocerciasis is endemic in 12 of the 14 health districts of Sierra Leone. Good treatment coverage of community-directed treatment with ivermectin was achieved between 2005 and 2009 after the 11-year civil conflict. Sentinel site surveys were conducted in 2010 to evaluate the impact of five annual rounds of ivermectin distribution. In total, 39 sentinel villages from hyper- and meso-endemic areas across the 12 endemic districts were surveyed using skin snips in 2010. Results were analyzed and compared with the baseline data from the same 39 villages. The average microfilaridermia (MF) prevalence across 39 sentinel villages was 53.10% at baseline. The MF prevalence was higher in older age groups, with the lowest in the age group of 1-9 years (11.00%) and the highest in the age group of 40-49 years (82.31%). Overall mean MF density among the positives was 28.87 microfilariae (mf)/snip, increasing with age with the lowest in the age group of 1-9 years and the highest in the age group of 40-49 years. Males had higher MF prevalence and density than females. In 2010 after five rounds of mass drug administration, the overall MF prevalence decreased by 60.26% from 53.10% to 21.10%; the overall mean MF density among the positives decreased by 71.29% from 28.87 mf/snip to 8.29 mf/snip; and the overall mean MF density among all persons examined decreased by 88.58% from 15.33 mf/snip to 1.75 mf/snip. Ten of 12 endemic districts had > 50% reduction in MF prevalence. Eleven of 12 districts had ≥50% reduction in mean MF density among the positives. A significant reduction of onchocerciasis MF prevalence and mean density was recorded in all 12 districts of Sierra Leone after five annual MDAs with effective treatment coverage. The results suggested that the onchocerciasis elimination programme in Sierra Leone was on course to reach the objective of eliminating onchocerciasis in the country by the year 2025. Annual MDA with ivermectin should continue in all 12 districts and

High sensitivity cascaded preamplifier with an optical bridge structure in Brillouin distributed fiber sensing system

NASA Astrophysics Data System (ADS)

Bi, Weihong; Lin, Hang; Fu, Xinghu; Fu, Guangwei

2013-12-01

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

The Surgical Workforce and Surgical Provider Productivity in Sierra Leone: A Countrywide Inventory.

PubMed

Bolkan, Håkon A; Hagander, Lars; von Schreeb, Johan; Bash-Taqi, Donald; Kamara, Thaim B; Salvesen, Øyvind; Wibe, Arne

2016-06-01

Limited data exist on surgical providers and their scope of practice in low-income countries (LICs). The aim of this study was to assess the distribution and productivity of all surgical providers in an LIC, and to evaluate correlations between the surgical workforce availability, productivity, rates, and volume of surgery at the district and hospital levels. Data on surgeries and surgical providers from 56 (93.3 %) out of 60 healthcare facilities providing surgery in Sierra Leone in 2012 were retrieved between January and May 2013 from operation theater logbooks and through interviews with key informants. The Sierra Leonean surgical workforce consisted of 164 full-time positions, equal to 2.7 surgical providers/100,000 inhabitants. Non-specialists performed 52.8 % of all surgeries. In rural areas, the densities of specialists and physicians were 26.8 and 6.3 times lower, respectively, compared with urban areas. The average individual productivity was 2.8 surgeries per week, and varied considerably between the cadres of surgical providers and locations. When excluding four centers that only performed ophthalmic surgery, there was a positive correlation between a facility's volume of surgery and the productivity of its surgical providers (r s = 0.642, p < 0.001). Less than half of all of the surgery in Sierra Leone is performed by specialists. Surgical providers were significantly more productive in healthcare facilities with higher volumes of surgery. If all surgical providers were as productive as specialists in the private non-profit sector (5.1 procedures/week), the national volume of surgery would increase by 85 %.

Getting the 'blues': the existence, diffusion and influence of pornography on young peoples' sexual health in Sierra Leone.

PubMed

Day, Andrea

2014-01-01

While substantial research has examined the effects of pornography on young people in developed societies, existing studies fall short in addressing how sexually-explicit material affects young people in developing countries. The importance of such knowledge increases as the globalising effects of technology expand young peoples' access and exposure to pornography. During the summer of 2012, a study was undertaken in Sierra Leone examining factors affecting young peoples' sexual and reproductive health. The research assessed the influence of HIV knowledge, communication about sex, civil war and contraception myths on sexual behaviours, while remaining open to unanticipated factors. During data collection, respondents identified pornography, also called blues, as an influential factor, detailing its newfound accessibility driven by improved access to information and communication technologies in the country. Respondents also addressed several presumed ways in which pornography impacts young peoples' decisions about sexual health. The following study examines perceived effects of young peoples' exposure to pornography based on existing literature. It then outlines the findings of research conducted in Sierra Leone, drawing on primary data from the respondents and relevant published literature and concludes with proposals for addressing its negative effects.

Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

NASA Astrophysics Data System (ADS)

Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

2008-11-01

The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

Factors Underlying Ebola Virus Infection Among Health Workers, Kenema, Sierra Leone, 2014–2015

PubMed Central

Senga, Mikiko; Pringle, Kimberly; Ramsay, Andrew; Brett-Major, David M.; Fowler, Robert A.; French, Issa; Vandi, Mohamed; Sellu, Josephine; Pratt, Christian; Saidu, Josephine; Shindo, Nahoko; Bausch, Daniel G.

2016-01-01

Background. Ebola virus disease (EVD) in health workers (HWs) has been a major challenge during the 2014–2015 outbreak. We examined factors associated with Ebola virus exposure and mortality in HWs in Kenema District, Sierra Leone. Methods. We analyzed data from the Sierra Leone National Viral Hemorrhagic Fever Database, contact tracing records, Kenema Government Hospital (KGH) staff and Ebola Treatment Unit (ETU) rosters, and burial logs. Results. From May 2014 through January 2015, 600 cases of EVD originated in Kenema District, including 92 (15%) HWs, 66 (72%) of whom worked at KGH. Among KGH medical staff and international volunteers, 18 of 62 (29%) who worked in the ETU developed EVD, compared with 48 of 83 (58%) who worked elsewhere in the hospital. Thirteen percent of HWs with EVD reported contact with EVD patients, while 27% reported contact with other infected HWs. The number of HW EVD cases at KGH declined roughly 1 month after implementation of a new triage system at KGH and the opening of a second ETU within the district. The case fatality ratio for HWs and non-HWs with EVD was 69% and 74%, respectively. Conclusions. The cluster of HW EVD cases in Kenema District is one of the largest ever reported. Most HWs with EVD had potential virus exposure both inside and outside of hospitals. Prevention measures for HWs must address a spectrum of infection risks in both formal and informal care settings as well as in the community. PMID:27193749

Bioaccumulation of lead, copper, iron, and zinc by fish in a transect of the Santa Catarina River in Cadereyta Jimenez, Nuevo Leon, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-09-01

Changes have been observed in the ichthyic species community, upriver in the San Juan River in Nuevo Leon, Mexico. A disappearance of Notropis amabilis, Notropis stramineus, Dionda episcopa and Campostoma anomalum and an increased mortality of Astyanax mexicanus, Lepomis macrochirus and Cichlasoma cyanoguttatum have been found. These changes were probably due to industrial and domestic discharges which produced high levels of lead, copper, iron and detergents in the water. The investigation reported here was done in order to detect the possible presence of lead, copper, iron and zinc in the river waters and also, to determine a probable bioaccumulation ofmore » these metals in fish species of the Santa Catarina River in the state of Nuevo Leon in northeastern Mexico, since this river transports domestic and industrial wastes of urban and suburban zones.« less

Highly sensitive distributed birefringence measurements based on a two-pulse interrogation of a dynamic Brillouin grating

NASA Astrophysics Data System (ADS)

Soto, Marcelo A.; Denisov, Andrey; Angulo-Vinuesa, Xabier; Martin-Lopez, Sonia; Thévenaz, Luc; Gonzalez-Herraez, Miguel

2017-04-01

A method for distributed birefringence measurements is proposed based on the interference pattern generated by the interrogation of a dynamic Brillouin grating (DBG) using two short consecutive optical pulses. Compared to existing DBG interrogation techniques, the method here offers an improved sensitivity to birefringence changes thanks to the interferometric effect generated by the reflections of the two pulses. Experimental results demonstrate the possibility to obtain the longitudinal birefringence profile of a 20 m-long Panda fibre with an accuracy of 10-8 using 16 averages and 30 cm spatial resolution. The method enables sub-metric and highly-accurate distributed temperature and strain sensing.

Low referral completion of rapid diagnostic test-negative patients in community-based treatment of malaria in Sierra Leone

PubMed Central

2011-01-01

Background Malaria is hyper-endemic and a major public health problem in Sierra Leone. To provide malaria treatment closer to the community, Médecins Sans Frontières (MSF) launched a community-based project where Community Malaria Volunteers (CMVs) tested and treated febrile children and pregnant women for malaria using rapid diagnostic tests (RDTs). RDT-negative patients and severely ill patients were referred to health facilities. This study sought to determine the referral rate and compliance of patients referred by the CMVs. Methods In MSF's operational area in Bo and Pujehun districts, Sierra Leone, a retrospective analysis of referral records was carried out for a period of three months. All referral records from CMVs and referral health structures were reviewed, compared and matched for personal data. The eligible study population included febrile children between three and 59 months and pregnant women in their second or third trimester with fever who were noted as having received a referral advice in the CMV recording form. Results The study results showed a total referral rate of almost 15%. During the study period 36 out of 2,459 (1.5%) referred patients completed their referral. There was a significant difference in referral compliance between patients with fever but a negative RDT and patients with signs of severe malaria. Less than 1% (21/2,442) of the RDT-negative patients with fever completed their referral compared to 88.2% (15/17) of the patients with severe malaria (RR = 0.010 95% CI 0.006 - 0.015). Conclusions In this community-based malaria programme, RDT-negative patients with fever were referred to a health structure for further diagnosis and care with a disappointingly low rate of referral completion. This raises concerns whether use of CMVs, with referral as backup in RDT-negative cases, provides adequate care for febrile children and pregnant women. To improve the referral completion in MSF's community-based malaria programme in Sierra

Low referral completion of rapid diagnostic test-negative patients in community-based treatment of malaria in Sierra Leone.

PubMed

Thomson, Anna; Khogali, Mohammed; de Smet, Martin; Reid, Tony; Mukhtar, Ahmed; Peterson, Stefan; von Schreeb, Johan

2011-04-17

Malaria is hyper-endemic and a major public health problem in Sierra Leone. To provide malaria treatment closer to the community, Médecins Sans Frontières (MSF) launched a community-based project where Community Malaria Volunteers (CMVs) tested and treated febrile children and pregnant women for malaria using rapid diagnostic tests (RDTs). RDT-negative patients and severely ill patients were referred to health facilities. This study sought to determine the referral rate and compliance of patients referred by the CMVs. In MSF's operational area in Bo and Pujehun districts, Sierra Leone, a retrospective analysis of referral records was carried out for a period of three months. All referral records from CMVs and referral health structures were reviewed, compared and matched for personal data. The eligible study population included febrile children between three and 59 months and pregnant women in their second or third trimester with fever who were noted as having received a referral advice in the CMV recording form. The study results showed a total referral rate of almost 15%. During the study period 36 out of 2,459 (1.5%) referred patients completed their referral. There was a significant difference in referral compliance between patients with fever but a negative RDT and patients with signs of severe malaria. Less than 1% (21/2,442) of the RDT-negative patients with fever completed their referral compared to 88.2% (15/17) of the patients with severe malaria (RR = 0.010 95% CI 0.006 - 0.015). In this community-based malaria programme, RDT-negative patients with fever were referred to a health structure for further diagnosis and care with a disappointingly low rate of referral completion. This raises concerns whether use of CMVs, with referral as backup in RDT-negative cases, provides adequate care for febrile children and pregnant women. To improve the referral completion in MSF's community-based malaria programme in Sierra Leone, and in similar community

An ultra-wideband tunable multi-wavelength Brillouin fibre laser based on a semiconductor optical amplifier and dispersion compensating fibre in a linear cavity configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zulkifli, M Z; Ahmad, H; Hassan, N A

2011-07-31

A multi-wavelength Brillouin fibre laser (MBFL) with an ultra-wideband tuning range from 1420 nm to 1620 nm is demonstrated. The MBFL uses an ultra-wideband semiconductor optical amplifier (SOA) and a dispersion compensating fibre (DCF) as the linear gain medium and nonlinear gain medium, respectively. The proposed MBFL has a wide tuning range covering the short (S-), conventional (C-) and long (L-) bands with a wavelength spacing of 0.08 nm, making it highly suitable for DWDM system applications. The output power of the observed Brillouin Stokes ranges approximately from -5.94 dBm to -0.41 dBm for the S-band, from -4.34 dBm tomore » 0.02 dBm for the C-band and from -2.19 dBm to 0.39 dBm for the L-band. The spacing between each adjacent wavelengths of all the three bands is about 0.08 nm, which is approximately 10.7 GHz for the frequency domain. (lasers)« less

Review: Leon N. Cooper’s Science and Human Experience: Values, Culture, and the Mind

PubMed Central

Lynch, Gary S.

2015-01-01

Why are we reviewing a book written by someone who shared in the 1972 Nobel Prize in Physics for work on superconductivity? Because shortly after winning the prize, Leon N. Cooper transitioned into brain research—specifically, the biological basis of memory. He became director of the Brown University Institute for Brain and Neural Systems, whose interdisciplinary program allowed him to integrate research on the brain, physics, and even philosophy. His new book tackles a diverse spectrum of topics and questions, including these: Does science have limits? Where does order come from? Can we understand consciousness? PMID:27358665

Building capacity for skilled birth attendance: An evaluation of the Maternal and Child Health Aides training programme in Sierra Leone.

PubMed

Jones, Susan; Ameh, Charles A; Gopalakrishnan, Somasundari; Sam, Betty; Bull, Florence; Labicane, Roderick R; Dabo, Fatmata; van den Broek, Nynke

2015-12-01

Maternal and Child Health Aides (MCH Aide) in Sierra Leone provide the majority of maternity services at primary care level. To formulate recommendations for improving the quality and scale-up of MCH Aides training an evaluation of all schools across Sierra Leone was undertaken. Structured, direct observation of two randomly selected teaching sessions per school using pre-tested standardised review forms. Event sampling with random selection of timetabled sessions across all 14 MCH Aide Training Schools. All MCH Aide training schools across Sierra Leone. Tutors across 14 MCH Aide training schools observed in August 2013. Assessment of four key elements of teaching and learning: (1) teaching style, (2) use of visual aids, (3) teaching environment and (4) student involvement. In the majority of teaching schools there was over-crowding (11/14), lack of furniture and inconsistent electricity supply. Ten of 26 tutors used lesson plans and teaching was mostly tutor- rather than student-focused. Majority of tutors use a didactic approach rather than active learning methods. Teaching aides were rarely available (15% of lessons). Tutors were knowledgeable in their subject area and there was evidence of an excellent tutor-student relationship. Training for Maternal and Child health Aides relies on teacher focused didactic methods, which may hinder student learning. Teaching and learning within the schools needs to be enhanced by a combination of tutor development and improvements in the learning environment. Interventions to improve the quality of teaching are urgently needed and should include training on teaching techniques and student assessment for tutors, provision of audio visual equipment and teaching aides such as posters and mannequins. Monitoring and Evaluation of interventions is critical to be able to amend the programmes approach and address further challenges at an early stage. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

The Ebola virus disease outbreak and the mineral sectors of Guinea, Liberia, and Sierra Leone

USGS Publications Warehouse

Bermúdez-Lugo, Omayra; Menzie, William D.

2015-01-01

In response to the uncertainty surrounding the status of mineral projects in Guinea, Liberia, and Sierra Leone, the National Minerals Information Center compiled information on the distribution of mines, mineral facilities, and mineral projects under development in the three countries. This fact sheet provides information on the role that the mineral sector plays in their respective economies, on the operating status of mining projects through yearend 2014, and on the coordinated actions by mining companies to support governments and international relief organizations in their efforts to contain the EVD outbreak.

Single laser pulse compression via strongly coupled stimulated Brillouin scattering in plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, H.; Wu, Z. H.; Zhang, Z. M.

2016-07-15

Laser amplification in plasma, including stimulated Raman scattering amplification and strongly coupled stimulated Brillouin scattering (sc-SBS) amplification, is very promising to generate ultrahigh-power and ultrashort laser pulses. But both are quite complex in experiments: at least three different laser pulses must be prepared; temporal delay and spatial overlap of these three pulses are difficult. We propose a single pulse compression scheme based on sc-SBS in plasma. Only one moderately long laser is applied, the front part of which ionizes the gas to produced plasma, and gets reflected by a plasma mirror at the end of the gas channel. The reflectedmore » front quickly depletes the remaining part of the laser by sc-SBS in the self-similar regime. The output laser is much stronger and shorter. This scheme is at first considered theoretically, then validated by using 1D PIC simulations.« less

Stimulated Brillouin scattering in ultra-long distributed feedback Bragg gratings in standard optical fiber.

PubMed

Loranger, Sébastien; Lambin-Iezzi, Victor; Wahbeh, Mamoun; Kashyap, Raman

2016-04-15

Distributed feedback (DFB) fiber Bragg gratings (FBG) are widely used as narrow-band filters and single-mode cavities for lasers. Recently, a nonlinear generation has been shown in 10-20 cm DFB gratings in a highly nonlinear fiber. First, we show in this Letter a novel fabrication technique of ultra-long DFBs in a standard fiber (SMF-28). Second, we demonstrate nonlinear generation in such gratings. A particular inscription technique was used to fabricate all-in-phase ultra-long FBG and to implement reproducible phase shift to form a DFB mode. We demonstrate stimulated Brillouin scattering (SBS) emission from this DFB mode and characterize the resulting laser. It seems that such a SBS based DFB laser stabilizes a pump's jittering and reduces its linewidth.

The Role of Non-Governmental Organisations and Faith-Based Organisations in Achieving Education for All: The Case of Sierra Leone

ERIC Educational Resources Information Center

Nishimuko, Mikako

2009-01-01

Sierra Leone, one of the world's poorest countries, experienced a civil war from 1991 to 2002. The government's capacity to provide educational services remains weak, and still over 30% of children in the country are hard to reach and do not have access to primary education. This paper discusses the role of non-governmental organisations (NGOs)…

Novel Retinal Lesion in Ebola Survivors, Sierra Leone, 2016

PubMed Central

Scott, Janet T.; Baxter, Julia M.; Parkes, Craig K.; Dwivedi, Rahul; Czanner, Gabriela; Vandy, Matthew J.; Momorie, Fayiah; Fornah, Alimamy D.; Komba, Patrick; Richards, Jade; Sahr, Foday; Beare, Nicholas A.V.; Semple, Malcolm G.

2017-01-01

We conducted a case–control study in Freetown, Sierra Leone, to investigate ocular signs in Ebola virus disease (EVD) survivors. A total of 82 EVD survivors with ocular symptoms and 105 controls from asymptomatic civilian and military personnel and symptomatic eye clinic attendees underwent ophthalmic examination, including widefield retinal imaging. Snellen visual acuity was <6/7.5 in 75.6% (97.5% CI 63%–85.7%) of EVD survivors and 75.5% (97.5% CI 59.1%–87.9%) of controls. Unilateral white cataracts were present in 7.4% (97.5% CI 2.4%–16.7%) of EVD survivors and no controls. Aqueous humor from 2 EVD survivors with cataract but no anterior chamber inflammation were PCR-negative for Zaire Ebola virus, permitting cataract surgery. A novel retinal lesion following the anatomic distribution of the optic nerve axons occurred in 14.6% (97.5% CI 7.1%–25.6%) of EVD survivors and no controls, suggesting neuronal transmission as a route of ocular entry. PMID:28628441

Performance analysis of the GR712RC dual-core LEON3FT SPARC V8 processor in an asymmetric multi-processing environment

NASA Astrophysics Data System (ADS)

Giusi, Giovanni; Liu, Scige J.; Galli, Emanuele; Di Giorgio, Anna M.; Farina, Maria; Vertolli, Nello; Di Lellis, Andrea M.

2016-07-01

In this paper we present the results of a series of performance tests carried out on a prototype board mounting the Cobham Gaisler GR712RC Dual Core LEON3FT processor. The aim was the characterization of the performances of the dual core processor when used for executing a highly demanding lossless compression task, acting on data segments continuously copied from the static memory to the processor RAM. The selection of the compression activity to evaluate the performances was driven by the possibility of a comparison with previously executed tests on the Cobham/Aeroflex Gaisler UT699 LEON3FT SPARC™ V8. The results of the test activity have shown a factor 1.6 of improvement with respect to the previous tests, which can easily be improved by adopting a faster onboard board clock, and provided indications on the best size of the data chunks to be used in the compression activity.

Strengthening Health Systems While Responding to a Health Crisis: Lessons Learned by a Nongovernmental Organization During the Ebola Virus Disease Epidemic in Sierra Leone

PubMed Central

Cancedda, Corrado; Davis, Sheila M.; Dierberg, Kerry L.; Lascher, Jonathan; Kelly, J. Daniel; Barrie, Mohammed Bailor; Koroma, Alimamy Philip; George, Peter; Kamara, Adikali Alpha; Marsh, Ronald; Sumbuya, Manso S.; Nutt, Cameron T.; Scott, Kirstin W.; Thomas, Edgar; Bollbach, Katherine; Sesay, Andrew; Barrie, Ahmidu; Barrera, Elizabeth; Barron, Kathryn; Welch, John; Bhadelia, Nahid; Frankfurter, Raphael G.; Dahl, Ophelia M.; Das, Sarthak; Rollins, Rebecca E.; Eustis, Bryan; Schwartz, Amanda; Pertile, Piero; Pavlopoulos, Ilias; Mayfield, Allan; Marsh, Regan H.; Dibba, Yusupha; Kloepper, Danielle; Hall, Andrew; Huster, Karin; Grady, Michael; Spray, Kimberly; Walton, David A.; Daboh, Fodei; Nally, Cora; James, Sahr; Warren, Gabriel S.; Chang, Joyce; Drasher, Michael; Lamin, Gina; Bangura, Sherry; Miller, Ann C.; Michaelis, Annie P.; McBain, Ryan; Broadhurst, M. Jana; Murray, Megan; Richardson, Eugene T.; Philip, Ted; Gottlieb, Gary L.; Mukherjee, Joia S.; Farmer, Paul E.

2016-01-01

An epidemic of Ebola virus disease (EVD) beginning in 2013 has claimed an estimated 11 310 lives in West Africa. As the EVD epidemic subsides, it is important for all who participated in the emergency Ebola response to reflect on strengths and weaknesses of the response. Such reflections should take into account perspectives not usually included in peer-reviewed publications and after-action reports, including those from the public sector, nongovernmental organizations (NGOs), survivors of Ebola, and Ebola-affected households and communities. In this article, we first describe how the international NGO Partners In Health (PIH) partnered with the Government of Sierra Leone and Wellbody Alliance (a local NGO) to respond to the EVD epidemic in 4 of the country's most Ebola-affected districts. We then describe how, in the aftermath of the epidemic, PIH is partnering with the public sector to strengthen the health system and resume delivery of regular health services. PIH's experience in Sierra Leone is one of multiple partnerships with different stakeholders. It is also one of rapid deployment of expatriate clinicians and logistics personnel in health facilities largely deprived of health professionals, medical supplies, and physical infrastructure required to deliver health services effectively and safely. Lessons learned by PIH and its partners in Sierra Leone can contribute to the ongoing discussion within the international community on how to ensure emergency preparedness and build resilient health systems in settings without either. PMID:27688219

Potential human health risk by 234,238U and 210Po due to consumption of fish from the "Luis L. Leon" reservoir (Northern Mexico)

NASA Astrophysics Data System (ADS)

Luna-Porres, M. Y.; Rodríguez-Villa, M. A.; Herrera-Peraza, E.; Cabral-Lares, M.; Renteria-Villalobos, M.; Montero-Cabrera, M. E.

2014-07-01

The Conchos River is one of the most important in northern Mexico and the main surface waterway in the arid state of Chihuahua. The Luis L. Leon dam produces the Luis L. Leon Reservoir, which is the last major reservoir before the Conchos River enters the Rio Grande at the Texas-Chihuahua border. Activity concentrations (AC) of 234,238U and 210Po in fillet and liver of three stocked fish species (Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus), as well as in water from the Luis L. Leon reservoir were determined. 238U and 234U ACs in fillet samples showed values of 0.007-0.014 and 0.01-0.02 Bq kg-1 wet weight (ww), respectively. Liver samples for Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus species, present 210Po AC of 1.16-3.26 0.70-1.13 and 0.93-1.37 Bqṡkg-1 ww. The elemental Bioaccumulation Factor (BAF) for fish tissues respect to their concentrations in water was determined. Lepomis cyanellus species showed the highest BAF for total uranium in fillet, with value 1.5. The annual effective dose for uranium in adults by fish consumption in this work ranged from 4.46×10-3 to 3.68×10-2 μSvṡyear-1. The difference in concentrations of uranium in fillet among the studied species is likely primarily due to their differences in diet and habitat.

Prevalence of Autism Spectrum Disorders in Guanajuato, Mexico: The Leon survey.

PubMed

Fombonne, Eric; Marcin, Carlos; Manero, Ana Cecilia; Bruno, Ruth; Diaz, Christian; Villalobos, Michele; Ramsay, Katrina; Nealy, Benjamin

2016-05-01

There are no epidemiological data on autism for Mexico. This study was conducted to generate a first estimate of ASD prevalence in Mexico. We surveyed children age eight in Leon (Guanajuato). The sample was stratified in two strata: (1) children having special education and medical records (SEMR; N = 432) and (2) children attending regular schools (GSS; N = 11,684). GSS children were screened with the SRS and those with the highest scores were invited to a diagnostic evaluation. The final sample comprised 36 children (80.6 % male) who had confirmed ASD. A third had intellectual disability, 25 % were non-verbal, 69 % had co-occurring behavioral problems. The prevalence overall was 0.87 % (95 % CI 0.62, 1.1 %). This survey provides an estimate for ASD prevalence in Mexico that is consistent with recent studies.

Ebola Virus Disease in Children, Sierra Leone, 2014–2015

PubMed Central

Naveed, Asad; Wing, Kevin; Gbessay, Musa; Ross, J.C.G.; Checchi, Francesco; Youkee, Daniel; Jalloh, Mohammed Boie; Baion, David; Mustapha, Ayeshatu; Jah, Hawanatu; Lako, Sandra; Oza, Shefali; Boufkhed, Sabah; Feury, Reynold; Bielicki, Julia A.; Gibb, Diana M.; Klein, Nigel; Sahr, Foday; Yeung, Shunmay

2016-01-01

Little is known about potentially modifiable factors in Ebola virus disease in children. We undertook a retrospective cohort study of children <13 years old admitted to 11 Ebola holding units in the Western Area, Sierra Leone, during 2014–2015 to identify factors affecting outcome. Primary outcome was death or discharge after transfer to Ebola treatment centers. All 309 Ebola virus–positive children 2 days–12 years old were included; outcomes were available for 282 (91%). Case-fatality was 57%, and 55% of deaths occurred in Ebola holding units. Blood test results showed hypoglycemia and hepatic/renal dysfunction. Death occurred swiftly (median 3 days after admission) and was associated with younger age and diarrhea. Despite triangulation of information from multiple sources, data availability was limited, and we identified no modifiable factors substantially affecting death. In future Ebola virus disease epidemics, robust, rapid data collection is vital to determine effectiveness of interventions for children. PMID:27649367

Detection of a typhus group Rickettsia in Amblyomma ticks in the state of Nuevo Leon, Mexico.

PubMed

Medina-Sanchez, Aaron; Bouyer, Donald H; Alcantara-Rodriguez, Virginia; Mafra, Claudio; Zavala-Castro, Jorge; Whitworth, Ted; Popov, Vsevolod L; Fernandez-Salas, Ildefonso; Walker, David H

2005-12-01

The state of Nuevo Leon, Mexico has had outbreaks of typhus group rickettsiosis, most recently recognized in 1997. Evaluation of the sera of 345 patients with a dengue-like illness revealed that 25.5% had antibodies reactive with typhus group rickettsiae and 16% had antibodies to Rickettsia parkeri. Rickettsiae were detected by PCR and shell-vial isolations in the field-collected Amblyomma ticks. Molecular characterization by DNA sequence analysis of the gltA, ompB, and 17-kDa gene identified the organisms to be R. prowazekii.

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

NASA Astrophysics Data System (ADS)

Fu, H. Y.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Ruohoniemi, J. M.

2015-08-01

Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Stimulated Raman and Brillouin scattering of polarization-smoothed and temporally smoothed laser beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, R.L.; Lefebvre, E.; Langdon, A.B.

1999-04-01

Control of filamentation and stimulated Raman and Brillouin scattering is shown to be possible by use of both spatial and temporal smoothing schemes. The spatial smoothing is accomplished by the use of phase plates [Y. Kato and K. Mima, Appl. Phys. {bold 329}, 186 (1982)] and polarization smoothing [Lefebvre {ital et al.}, Phys. Plasmas {bold 5}, 2701 (1998)] in which the plasma is irradiated with two orthogonally polarized, uncorrelated speckle patterns. The temporal smoothing considered here is smoothing by spectral dispersion [Skupsky {ital et al.}, J. Appl. Phys. {bold 66}, 3456 (1989)] in which the speckle pattern changes on themore » laser coherence time scale. At the high instability gains relevant to laser fusion experiments, the effect of smoothing must include the competition among all three instabilities. {copyright} {ital 1999 American Institute of Physics.}« less

Food deserts in Leon County, FL: disparate distribution of Supplemental Nutrition Assistance Program-accepting stores by neighborhood characteristics.

PubMed

Rigby, Samantha; Leone, Angela F; Kim, Hwahwan; Betterley, Connie; Johnson, Mary Ann; Kurtz, Hilda; Lee, Jung Sun

2012-01-01

Examine whether neighborhood characteristics of racial composition, income, and rurality were related to distribution of Supplemental Nutrition Assistance Program (SNAP)-accepting stores in Leon County, Florida. Cross-sectional; neighborhood and food store data collected in 2008. Forty-eight census tracts as proxy of neighborhoods in Leon County, Florida. All stores and SNAP-accepting stores were identified from a commercial business directory and a United States Department of Agriculture SNAP-accepting store list, respectively (n = 288). Proportion of SNAP-accepting stores across neighborhoods. Descriptive statistics to describe distribution of SNAP-accepting stores by neighborhood characteristics. Proportions of SNAP-accepting stores were compared by neighborhood characteristics with Wilcoxon-Mann-Whitney and Kruskal-Wallis tests. Of 288 available stores, 45.1% accepted SNAP benefits. Of the 48 neighborhoods, 16.7% had no SNAP-accepting stores. Proportions of SNAP-accepting grocery stores were significantly different by neighborhood racial composition and income. Primarily black neighborhoods did not have any supermarkets. Results were mixed with regard to distribution of food stores and SNAP-accepting stores by neighborhood racial composition, income, and rurality. This study suggests disparities in distribution of SNAP-accepting stores across neighborhood characteristics of racial composition, income, and rurality. Copyright © 2012 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.

Safety of a condom uterine balloon tamponade (ESM-UBT) device for uncontrolled primary postpartum hemorrhage among facilities in Kenya and Sierra Leone.

PubMed

Ramanathan, Aparna; Eckardt, Melody J; Nelson, Brett D; Guha, Moytrayee; Oguttu, Monica; Altawil, Zaid; Burke, Thomas

2018-05-15

Postpartum hemorrhage is the leading cause of maternal mortality in low- and middle-income countries. While evidence on uterine balloon tamponade efficacy for severe hemorrhage is encouraging, little is known about safety of this intervention. The objective of this study was to evaluate the safety of an ultra-low-cost uterine balloon tamponade package (named ESM-UBT) for facility-based management of uncontrolled postpartum hemorrhage (PPH) in Kenya and Sierra Leone. Data were collected on complications/adverse events in all women who had an ESM-UBT device placed among 92 facilities in Sierra Leone and Kenya, between September 2012 and December 2015, as part of a multi-country study. Three expert maternal health investigator physicians analyzed each complication/adverse event and developed consensus on whether there was a potential causal relationship associated with use of the ESM-UBT device. Adverse events/complications specifically investigated included death, hysterectomy, uterine rupture, perineal or cervical injury, serious or minor infection, and latex allergy/anaphylaxis. Of the 201 women treated with an ESM-UBT device in Kenya and Sierra Leone, 189 (94.0%) survived. Six-week or longer follow-up was recorded in 156 of the 189 (82.5%). A causal relationship between use of an ESM-UBT device and one death, three perineal injuries and one case of mild endometritis could not be completely excluded. Three experts found a potential association between these injuries and an ESM-UBT device highly unlikely. The ESM-UBT device appears safe for use in women with uncontrolled PPH. Trial registration was not completed as data was collected as a quality assurance measure for the ESM-UBT kit.

Elasticity of the eye's crystalline lens: A Brillouin light scattering study.

NASA Astrophysics Data System (ADS)

Bailey, S.; Gump, J.; Sooryakumar, R.; Jayaprakash, C.; Venkiteshwar, M. S.; Bullimore, M.; Twa, M.

2009-03-01

Focusing the eye on a near object results in an increase in its optical power brought about by contraction of the ciliary muscles and an increase in the lens surface curvature. Distant vision occurs when the muscular force flattens the lens. Central to the ability of the lens to alter shape are its mechanical properties. Thus, given that hardening of the lens would impede deformation and reduce its ability to undergo the changes required for accommodation, a noninvasive approach to measure the elastic properties of the lens is valuable. We present results of Brillouin scattering from bovine and human lenses (from the organ donor program at The Ohio State University) that measure their high frequency acoustic response. These measurements are conducted with a few milli-watts of laser power and, in the case of bovine lenses, from entire intact eye globes, allow the stiffness of the lens to be mapped across its cross-section. The results will be compared to values of the shear- and bulk-moduli determined from other techniques and the implications of differences in these moduli discussed.

Hemispherical Brillouin zone imaging of a diamond-type biological photonic crystal

PubMed Central

Wilts, Bodo D.; Michielsen, Kristel; De Raedt, Hans; Stavenga, Doekele G.

2012-01-01

The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material. PMID:22188768

Temperature Dependence of Brillouin Light Scattering Spectra of Acoustic Phonons in Silicon

NASA Astrophysics Data System (ADS)

Somerville, Kevin; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

2015-03-01

Thermal management represents an outstanding challenge in many areas of technology. Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. Interest in non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report temperature dependent BLS spectra of silicon, with Raman spectra taken simultaneously for comparison. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons. We determine that the integrated BLS intensity can be used measure the temperature of specific acoustic phonon modes. This work is supported by National Science Foundation (NSF) Thermal Transport Processes Program under Grant CBET-1336968.

Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations

NASA Astrophysics Data System (ADS)

Banerjee, Chandrima; Gruszecki, Pawel; Klos, Jaroslaw W.; Hellwig, Olav; Krawczyk, Maciej; Barman, Anjan

2017-07-01

By combining Brillouin light scattering and micromagnetic simulations, we studied the spin-wave (SW) dynamics of a Co/Pd thin film multilayer, which features a stripe domain structure at remanence. The periodic up and down domains are separated by corkscrew type domain walls. The existence of these domains causes a scattering of the otherwise bulk and surface SW modes, which form mode families, similar to a one-dimensional magnonic crystal. The dispersion relation and mode profiles of SWs are measured for the transferred wave vector parallel and perpendicular to the domain axis.

Suppression of stimulated Brillouin scattering in optical fibers using a linearly chirped diode laser.

PubMed

White, J O; Vasilyev, A; Cahill, J P; Satyan, N; Okusaga, O; Rakuljic, G; Mungan, C E; Yariv, A

2012-07-02

The output of high power fiber amplifiers is typically limited by stimulated Brillouin scattering (SBS). An analysis of SBS with a chirped pump laser indicates that a chirp of 2.5 × 10(15) Hz/s could raise, by an order of magnitude, the SBS threshold of a 20-m fiber. A diode laser with a constant output power and a linear chirp of 5 × 10(15) Hz/s has been previously demonstrated. In a low-power proof-of-concept experiment, the threshold for SBS in a 6-km fiber is increased by a factor of 100 with a chirp of 5 × 10(14) Hz/s. A linear chirp will enable straightforward coherent combination of multiple fiber amplifiers, with electronic compensation of path length differences on the order of 0.2 m.

Geophysical Remote Sensing Using the HF Pumped Stimulated Brillouin Scatter (SBS) Emission Lines Produced by HAARP

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Selcher, C. A.

2009-12-01

An ordinary or extraordinary mode electromagnetic wave can decay into a low frequency electrostatic wave and a scattered electromagnetic wave by a process called stimulated Brillouin scatter (SBS). The low frequency wave can be either an ion acoustic wave (IA) or an electrostatic ion cyclotron (EIC) wave. The first detection ion acoustic waves by this process during ionospheric modification with high power radio waves was reported by Norin et al. (2009) using the HAARP transmitter in Alaska. The first detection of the electrostatic ion cyclotron waves is reported here using HAARP during the March 2009 campaign. Subsequent experiments have provided additional verification of the SBS process and quantitative interpretation of the scattered wave frequency offsets to yield measurements of the electron temperatures in the heated ionosphere by Bernhardt et al. (2009). Using the SBS technique to generate ion acoustic waves, electron temperatures between 3000 and 4000 K were measured over the HAARP facility. The matching conditions for decay of the high frequency pump wave show that in addition to the production of an ion-acoustic wave, an electrostatic ion cyclotron wave can produced by the generalized SBS processes only if the pump waves makes a large angle with the magnetic field. When the EIC mode is produced, it is seen as a narrow of stimulated electromagnetic emissions at the ion cyclotron frequency. Occasionally, multiple lines are seen and analyzed to yield the relative abundance of oxygen, and molecular ions in the lower ionosphere. This ion mass spectrometer interpretation of the SBS data is new to the field of ionosphere remote sensing. In addition, based on the matching condition theory, the first profiles of the scattered wave amplitude are produced using the stimulated Brillouin scatter (SBS) matching conditions. These profiles are consistent with maximum ionospheric interactions at the upper-hybrid resonance height and at a region just below the plasma

Does Community Poverty Reduce Children's School Attendance More at Primary Education than at Secondary Education? Evidence from Post-Conflict Sierra Leone

ERIC Educational Resources Information Center

Kamanda, Mamusu

2016-01-01

In Sierra Leone, the number of primary schools is almost seven times more than junior-secondary schools (JSS). Living in a poor community has been shown to reduce children's school attendance because of lower access and poorer quality of education in these communities. However, it is unclear whether living in a poor community reduces attendance at…

Strengthening Health Systems While Responding to a Health Crisis: Lessons Learned by a Nongovernmental Organization During the Ebola Virus Disease Epidemic in Sierra Leone.

PubMed

Cancedda, Corrado; Davis, Sheila M; Dierberg, Kerry L; Lascher, Jonathan; Kelly, J Daniel; Barrie, Mohammed Bailor; Koroma, Alimamy Philip; George, Peter; Kamara, Adikali Alpha; Marsh, Ronald; Sumbuya, Manso S; Nutt, Cameron T; Scott, Kirstin W; Thomas, Edgar; Bollbach, Katherine; Sesay, Andrew; Barrie, Ahmidu; Barrera, Elizabeth; Barron, Kathryn; Welch, John; Bhadelia, Nahid; Frankfurter, Raphael G; Dahl, Ophelia M; Das, Sarthak; Rollins, Rebecca E; Eustis, Bryan; Schwartz, Amanda; Pertile, Piero; Pavlopoulos, Ilias; Mayfield, Allan; Marsh, Regan H; Dibba, Yusupha; Kloepper, Danielle; Hall, Andrew; Huster, Karin; Grady, Michael; Spray, Kimberly; Walton, David A; Daboh, Fodei; Nally, Cora; James, Sahr; Warren, Gabriel S; Chang, Joyce; Drasher, Michael; Lamin, Gina; Bangura, Sherry; Miller, Ann C; Michaelis, Annie P; McBain, Ryan; Broadhurst, M Jana; Murray, Megan; Richardson, Eugene T; Philip, Ted; Gottlieb, Gary L; Mukherjee, Joia S; Farmer, Paul E

2016-10-15

An epidemic of Ebola virus disease (EVD) beginning in 2013 has claimed an estimated 11 310 lives in West Africa. As the EVD epidemic subsides, it is important for all who participated in the emergency Ebola response to reflect on strengths and weaknesses of the response. Such reflections should take into account perspectives not usually included in peer-reviewed publications and after-action reports, including those from the public sector, nongovernmental organizations (NGOs), survivors of Ebola, and Ebola-affected households and communities. In this article, we first describe how the international NGO Partners In Health (PIH) partnered with the Government of Sierra Leone and Wellbody Alliance (a local NGO) to respond to the EVD epidemic in 4 of the country's most Ebola-affected districts. We then describe how, in the aftermath of the epidemic, PIH is partnering with the public sector to strengthen the health system and resume delivery of regular health services. PIH's experience in Sierra Leone is one of multiple partnerships with different stakeholders. It is also one of rapid deployment of expatriate clinicians and logistics personnel in health facilities largely deprived of health professionals, medical supplies, and physical infrastructure required to deliver health services effectively and safely. Lessons learned by PIH and its partners in Sierra Leone can contribute to the ongoing discussion within the international community on how to ensure emergency preparedness and build resilient health systems in settings without either. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America.

Biomechanics of fibrous proteins of the extracellular matrix studied by Brillouin scattering

PubMed Central

Palombo, Francesca; Winlove, C. Peter; Edginton, Ryan S.; Green, Ellen; Stone, Nick; Caponi, Silvia; Madami, Marco; Fioretto, Daniele

2014-01-01

Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure–function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin—the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young's, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at

Inhibition of stimulated Raman scattering due to the excitation of stimulated Brillouin scattering

NASA Astrophysics Data System (ADS)

Zhao, Yao; Yu, Lu-Le; Weng, Su-Ming; Ren, Chuang; Liu, Chuan-Sheng; Sheng, Zheng-Ming

2017-09-01

The nonlinear coupling between stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) of intense laser in underdense plasma is studied theoretically and numerically. Based upon the fluid model, their coupling equations are derived, and a threshold condition of plasma density perturbations due to SBS for the inhibition of SRS is given. Particle-in-cell simulations show that this condition can be achieved easily by SBS in the so-called fluid regime with kLλD<0.15 , where kL is the Langmuir wave number and λD is the Debye length [Kline et al., Phys. Plasmas 13, 055906 (2006)]. SBS can reduce the saturation level of SRS and the temperature of electrons in both homogeneous and inhomogeneous plasma. Numerical simulations also show that this reduced SRS saturation is retained even if the fluid regime condition mentioned above is violated at a later time due to plasma heating.

Demonstrating the saturation of stimulated Brillouin scattering by ion acoustic decay using fully kinetic simulations

DOE PAGES

Chapman, T.; Winjum, B. J.; Brunner, S.; ...

2015-09-01

The saturation of stimulated Brillouin scattering (SBS) by the decay to turbulence of the ion acoustic wave (IAW) that participates in the three-wave SBS interaction is demonstrated using a quasi-noiseless one-dimensional numerical solution to the Vlasov-Maxwell system of equations. This simulation technique permits careful examination of the decay process and its role in the complex evolution of SBS. Here, the IAW decay process is shown to be an effective SBS saturation mechanism. In our example, the instantaneous plasma reflectivity saturates at ~30% and drops to ~0% as a direct consequence of IAW decay. A contrasting example where the reflectivity ismore » controlled by dephasing due to the nonlinear frequency of the IAW is also discussed.« less

Context matters: Community characteristics and mental health among war-affected youth in Sierra Leone

PubMed Central

Betancourt, Theresa S.; McBain, Ryan; Newnham, Elizabeth A.; Brennan, Robert T.

2013-01-01

Background Worldwide, over one billion children and adolescents live in war-affected settings. At present, only limited research has investigated linkages between disrupted social ecology and adverse mental health outcomes among war-affected youth. In this study, we examine three community-level characteristics—social disorder and collective efficacy within the community, as reported by caregivers, and perceived stigma as reported by youth—in relation to externalizing behaviors and internalizing symptoms among male and female former child soldiers in post-conflict Sierra Leone. Methods 243 former child soldiers (30% female, mean age at baseline: 16.6 years) and their primary caregivers participated in interviews in 2004 and 2008, as part of a larger prospective cohort study of war-affected youth in Sierra Leone. Two-point growth models were estimated to examine the relationship between community-level characteristics and externalizing and internalizing outcomes across the time points. Results Both social disorder within the community, reported by caregivers, and perceived stigma, reported by youth, positively co-varied with youths’ externalizing and internalizing scores—indicating that higher levels of each at baseline and follow-up were associated with higher levels of mental health problems at both time points (p<0.05). The relationship between collective efficacy and mental health outcomes was non-significant (p>0.05). Conclusions This study offers a rare glimpse into the role that the post-conflict social context plays in shaping mental health among former child soldiers. Results indicate that both social disorder and perceived stigma within the community demonstrate an important relationship to externalizing and internalizing problems among adolescent ex-combatants. Moreover, these relationships persisted over a four-year period of follow up. These results underscore the importance of the post-conflict social environment and the need to develop post

Psychosocial support and resilience building among health workers in Sierra Leone: interrelations between coping skills, stress levels, and interpersonal relationships.

PubMed

Vesel, Linda; Waller, Kathryn; Dowden, Justine; Fotso, Jean Christophe

2015-01-01

In low- and middle-income countries, a shortage of properly trained, supervised, motivated and equitably distributed health workers often hinder the delivery of lifesaving interventions. Various health workforce bottlenecks can be addressed by tackling well-being and interpersonal relationships of health workers with their colleagues and clients. This paper uses data from the Helping Health Workers Cope (HHWC) project in a rural district of Sierra Leone to achieve three objectives. First, we describe the effect of counseling and psychosocial training on coping skills, stress levels, and provider-provider and provider-client relationships. Second, we examine whether a change in coping skills is associated with a change in relationships. Finally, we qualitatively identify key ways through which the uptake of coping skills is linked to a change in relationships. The HHWC project was implemented from February 2012 to June 2013 in Kono district in the Eastern province of Sierra Leone, with the neighboring district of Tonkolili selected as the control site. The evaluation followed a mixed-methods approach, which included a quantitative survey, in-depth interviews and focus group discussions with health workers and clients. Mean values of the variables of interest were compared across sub-populations, and correlation analyses were performed between changes in coping skills, stress levels, and changes in relationships. Overall, the results demonstrate that the HHWC intervention had a positive effect on coping skills, stress levels and provider-provider and provider-client relationships. Furthermore, associations were observed between changes in coping skills and changes in relationships as well as changes in stress management skills and changes in relationships. Psychosocial education can have major impacts on health worker well-being and the quality of health care delivery. Integrating psychosocial counseling and training interventions into health worker pre-service and

Air radioactivity levels following the Fukushima reactor accident measured at the Laboratoire Souterrain de Modane, France.

PubMed

Loaiza, P; Brudanin, V; Piquemal, F; Reyss, J-L; Stekl, I; Warot, G; Zampaolo, M

2012-12-01

The radioactivity levels in the air of the radionuclides released by the Fukushima accident were measured at the Laboratoire Souterrain de Modane, in the South-East of France, during the period 25 March-18 April 2011. Air-filters from the ventilation system exposed for one or two days were measured using low-background gamma-ray spectrometry. In this paper we present the activity concentrations obtained for the radionuclides (131)I, (132)Te, (134)Cs, (137)Cs, (95)Nb, (95)Zr, (106)Ru, (140)Ba/La and (103)Ru. The activity concentration of (131)I was of the order of 100 μBq/m(3), more than 100 times higher than the activities of other fission products. The highest activities of (131)I were measured as a first peak on 30 March and a second peak on 3-4 April. The activity concentrations of (134)Cs and (137)Cs varied from 5 to 30 μBq/m(3). The highest activity concentration recorded for Cs corresponded to the same period as for (131)I, with a peak on 2-3 April. The results of the radioactivity concentration levels in grass and mushrooms exposed to the air in the Modane region were also measured. Activity concentrations of (131)I of about 100 mBq/m(2) were found in grass. Copyright © 2012 Elsevier Ltd. All rights reserved.

HIV/AIDS practice patterns, knowledge, and educational needs among Hispanic clinicians in Texas, USA, and Nuevo Leon, Mexico.

PubMed

Martinez, J L; Licea Serrato, J de D; Jimenez, R; Grimes, R M

1998-07-01

Hispanic clinicians in Texas, United States of America, and in the neighboring state of Nuevo Leon, Mexico, were surveyed to determine their educational needs in the area of HIV/AIDS. Two-thirds of the 74 Texan and 22% of the 104 Mexican physicians queried had seen at least one HIV/AIDS patient in the previous year. The majority of the respondents were primary care physicians who: 1) were in private practice; 2) saw more than 1,000 patients per year; 3) had been out of training for more than 10 years; 4) provided some HIV prevention education to patients based on their perceived risk of infection; 5) rated their own knowledge of HIV/AIDS as average but rated their knowledge of treatments for the disease below average; 6) received most of their information about HIV/AIDS from journals rather than formal continuing education programs; 7) thought Hispanic patients had special needs with regard to HIV/AIDS care; and 8) were willing to attend education programs to improve their HIV/AIDS management skills. The greatest barriers to caring for HIV patients were lack of clinical knowledge and fear of infection. These results point to a need for a large-scale training program to improve the HIV/AIDS management skills of Hispanic clinicians in Texas and Nuevo Leon.

Rayleigh-Brillouin scattering in SF6 in the kinetic regime

NASA Astrophysics Data System (ADS)

Wang, Yuanqing; Yu, Yin; Liang, Kun; Marques, Wilson; van de Water, Willem; Ubachs, Wim

2017-02-01

Rayleigh-Brillouin spectral profiles are measured with a laser-based scatterometry setup for a 90° scattering angle at a high signal-to-noise ratio (r.m.s. noise below 0.15% w.r.t. peak intensity) in sulfur-hexafluoride gas for pressures in the range 0.2-5 bar and for a wavelength of λ = 403.0 nm. The high quality data are compared to a number of light scattering models in order to address the effects of rotational and vibrational relaxation. While the vibrational relaxation rate is so slow that vibration degrees of freedom remain frozen, rotations relax on time scales comparable to those of the density fluctuations. Therefore, the heat capacity, the thermal conductivity and the bulk viscosity are all frequency-dependent transport coefficients. This is relevant for the Tenti model that depends on the values chosen for these transport coefficients. This is not the case for the other two models considered: a kinetic model based on rough-sphere interactions, and a model based on fluctuating hydrodynamics. The deviations with the experiment are similar between the three different models, except for the hydrodynamic model at pressures p≲ 2bar . As all models are in line with the ideal gas law, we hypothesize the presence of real gas effects in the measured spectra.

Experimental observation of spontaneous depolarized guided acoustic-wave Brillouin scattering in side cores of a multicore fiber

NASA Astrophysics Data System (ADS)

Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro; Set, Sze Yun; Yamashita, Shinji

2018-06-01

Spontaneous depolarized guided acoustic-wave Brillouin scattering (GAWBS) was experimentally observed in one of the side cores of an uncoated multicore fiber (MCF). The frequency bandwidth in the side core was up to ∼400 MHz, which is 0.5 times that in the central core. The GAWBS spectrum of the side core of the MCF included intrinsic peaks, which had different acoustic resonance frequencies from those of the central core. In addition, the spontaneous depolarized GAWBS in the central/side core was unaffected by that in the other core. These results will lead to the development of polarization/phase modulators using an MCF.

Influence of stimulated Brillouin scattering on positioning accuracy of long-range dual Mach-Zehnder interferometric vibration sensors

NASA Astrophysics Data System (ADS)

He, Xiangge; Xie, Shangran; Cao, Shan; Liu, Fei; Zheng, Xiaoping; Zhang, Min; Yan, Han; Chen, Guocai

2016-11-01

The properties of noise induced by stimulated Brillouin scattering (SBS) in long-range interferometers and their influences on the positioning accuracy of dual Mach-Zehnder interferometric (DMZI) vibration sensing systems are studied. The SBS noise is found to be white and incoherent between the two arms of the interferometer in a 1-MHz bandwidth range. Experiments on 25-km long fibers show that the root mean square error (RMSE) of the positioning accuracy is consistent with the additive noise model for the time delay estimation theory. A low-pass filter can be properly designed to suppress the SBS noise and further achieve a maximum RMSE reduction of 6.7 dB.

Mapping deforestation and urban expansion in Freetown, Sierra Leone, from pre- to post-war economic recovery.

PubMed

Mansaray, Lamin R; Huang, Jingfeng; Kamara, Alimamy A

2016-08-01

Freetown, the capital of Sierra Leone has experienced vast land-cover changes over the past three decades. In Sierra Leone, however, availability of updated land-cover data is still a problem even for environmental managers. This study was therefore, conducted to provide up-to-date land-cover data for Freetown. Multi-temporal Landsat data at 1986, 2001, and 2015 were obtained, and a maximum likelihood supervised classification was employed. Eight land-cover classes or categories were recognized as follows: water, wetland, built-up, dense forest, sparse forest, grassland, barren, and mangrove. Land-cover changes were mapped via post-classification change detection. The persistence, gain, and loss of each land-cover class, and selected land conversions were also quantified. An overall classification accuracy of 87.3 % and a Kappa statistic of 0.85 were obtained for the 2015 map. From 1986 to 2015, water, built-up, grassland, and barren had net gains, whereas forests, wetlands, and mangrove had net loses. Conversion analyses among forests, grassland, and built-up show that built-up had targeted grassland and avoided forests. This study also revealed that, the overall land-cover change at 2001-2015 was higher (28.5 %) than that recorded at 1986-2001 (20.9 %). This is attributable to the population increase in Freetown and the high economic growth and infrastructural development recorded countrywide after the civil war. In view of the rapid land-cover change and its associated environmental impacts, this study recommends the enactment of policies that would strike a balance between urbanization and environmental sustainability in Freetown.

Traffic related deaths in Nuevo Leon, Mexico: causes and associated factors.

PubMed

Arreola-Rissa, Carlos; Santos-Guzmán, Jesús; Esquivel-Guzmán, Adol; Mock, Charles N

2008-01-01

The effects of alcohol on mortality due to motor vehicle accidents was studied. During the first semester of 2003, a sample of 243 fatality victims of traffic-related accidents and their blood alcohol levels were analyzed in the state of Nuevo Leon, Mexico. The age-adjusted mortality rate for traffic accidents was 8.9/100000 pop. (13.2 for males and 3.21 for females, per 100000). Fatal accidents were more common in the Metropolitan Area (MA). Fatalities were four times greater in males and the mean age was 34.7+/-18.2 years. Blood alcohol was detected in almost half of the victims who were drivers of the vehicles; the other cases of fatalities may be associated with road/car condition, weather and other factors. Alcohol intoxication levels were primarily associated with male drivers ages 16 to 45 (p=0.029); levels increased with age. In females, alcohol played a lesser role, affecting mostly ages 31 to 45 y (p=0.055).

Stimulated Brillouin scatter and stimulated ion Bernstein scatter during electron gyroharmonic heating experiments

NASA Astrophysics Data System (ADS)

Fu, H.; Scales, W. A.; Bernhardt, P. A.; Samimi, A.; Mahmoudian, A.; Briczinski, S. J.; McCarrick, M. J.

2013-09-01

Results of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power radio waves are reported. These results obtained at the High Frequency Active Auroral Research Program (HAARP) facility specifically considered the generation of Magnetized Stimulated Brillouin Scatter (MSBS) and Stimulated Ion Bernstein Scatter (SIBS) lines in the SEE spectrum when the transmitter frequency is near harmonics of the electron gyrofrequency. The heater antenna beam angle effect was investigated on MSBS in detail and shows a new spectral line postulated to be generated near the upper hybrid resonance region due to ion acoustic wave interaction. Frequency sweeping experiments near the electron gyroharmonics show for the first time the transition from MSBS to SIBS lines as the heater pump frequency approaches the gyroharmonic. Significantly far from the gyroharmonic, MSBS lines dominate, while close to the gyroharmonic, SIBS lines strengthen while MSBS lines weaken. New possibilities for diagnostic information are discussed in light of these new observations.

Numerical study of phase conjugation in stimulated Brillouin scattering from an optical waveguide

NASA Astrophysics Data System (ADS)

Lehmberg, R. H.

1983-05-01

Stimulated Brillouin scattering (SBS) in a multimode optical waveguide is examined, and the parameters that affect the wavefront conjugation fidelity are studied. The nonlinear propagation code is briefly described and the calculated quantities are defined. The parameter study in the low reflectivity limit is described, and the effects of pump depletion are considered. The waveguide produced significantly higher fidelities than the focused configuration, in agreement with several experimental studies. The light scattered back through the phase aberrator exhibited a farfield intenstiy profile closely matching that of the incident beam; however, the nearfield intensity exhibited large and rapid spatial inhomogeneities across the entire aberrator, even for conjugation fidelities as high as 98 percent. In the absence of pump depletion, the fidelity increased with average pump intensity for amplitude gains up to around e to the 10th and then decreased slowly and monotonically with higher intensity. For all cases, pump depletion significantly enhanced the fidelity of the wavefront conjugation by inhibiting the small-scale pulling effect.

Life is a Self-Organizing Machine Driven by the Informational Cycle of Brillouin

NASA Astrophysics Data System (ADS)

Michel, Denis

2013-04-01

Acquiring information is indisputably energy-consuming and conversely, the availability of information permits greater efficiency. Strangely, the scientific community long remained reluctant to establish a physical equivalence between the abstract notion of information and sensible thermodynamics. However, certain physicists such as Szilard and Brillouin proposed: (i) to give to information the status of a genuine thermodynamic entity ( k B T ln2 joules/bit) and (ii) to link the capacity of storing information inferred from correlated systems, to that of indefinitely increasing organization. This positive feedback coupled to the self-templating molecular potential could provide a universal basis for the spontaneous rise of highly organized structures, typified by the emergence of life from a prebiotic chemical soup. Once established, this mechanism ensures the longevity and robustness of life envisioned as a general system, by allowing it to accumulate and optimize microstate-reducing recipes, thereby giving rise to strong nonlinearity, decisional capacity and multistability. Mechanisms possibly involved in priming this cycle are proposed.

Brillouin light scattering as a probe for low frequency quasiparticles in solids

NASA Astrophysics Data System (ADS)

Klimovich, Nikita; Olson, Kevin; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

2015-03-01

In increasingly small electronic and spintronic devices, electrons, optical phonons, acoustic phonons, and magnons are often driven out of local thermal equilibrium. Thermal transport based on equilibrium dynamics does not adequately describe these systems necessitating a better understanding of non-equilibrium transport processes. Measuring the specific temperatures of the different energy carriers is therefore crucial in understanding the thermal transport. Brillouin light scattering (BLS) has recently been explored as a temperature sensor for low frequency acoustic phonons in glass, and also magnons in metallic and insulating ferromagnetic materials. We report the measured BLS spectra of acoustic phonons in Silicon at different temperatures. The temperature dependence of the BLS peak frequency, linewidth, and integrated intensity are examined to evaluate their potential uses as temperature sensors of acoustic phonons. We also observe a large nonequilibrium in phonon-magnon temperature in YIG under the effects of laser heating and thereby extract a value for the phonon-magnon coupling coefficient. This work is funded by the National Science Foundation and the Army Research Office.

Simulation of stimulated Brillouin scattering and stimulated Raman scattering in shock ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, L.; Li, J.; Liu, W. D.

2016-04-15

We study stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) in shock ignition by comparing fluid and particle-in-cell (PIC) simulations. Under typical parameters for the OMEGA experiments [Theobald et al., Phys. Plasmas 19, 102706 (2012)], a series of 1D fluid simulations with laser intensities ranging between 2 × 10{sup 15} and 2 × 10{sup 16 }W/cm{sup 2} finds that SBS is the dominant instability, which increases significantly with the incident intensity. Strong pump depletion caused by SBS and SRS limits the transmitted intensity at the 0.17n{sub c} to be less than 3.5 × 10{sup 15 }W/cm{sup 2}. The PIC simulations show similar physics but with higher saturationmore » levels for SBS and SRS convective modes and stronger pump depletion due to higher seed levels for the electromagnetic fields in PIC codes. Plasma flow profiles are found to be important in proper modeling of SBS and limiting its reflectivity in both the fluid and PIC simulations.« less

Brillouin light scattering study of spin waves in NiFe/Co exchange spring bilayer films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haldar, Arabinda; Banerjee, Chandrima; Laha, Pinaki

2014-04-07

Spin waves are investigated in Permalloy(Ni{sub 80}Fe{sub 20})/Cobalt(Co) exchange spring bilayer thin films using Brillouin light scattering (BLS) experiment. The magnetic hysteresis loops measured by magneto-optical Kerr effect show a monotonic decrease in coercivity of the bilayer films with increasing Py thickness. BLS study shows two distinct modes, which are modelled as Damon-Eshbach and perpendicular standing wave modes. Linewidths of the frequency peaks are found to increase significantly with decreasing Py layer thickness. Interfacial roughness causes to fluctuate exchange coupling at the nanoscale regimes and the effect is stronger for thinner Py films. A quantitative analysis of the magnon linewidthsmore » shows the presence of strong local exchange coupling field which is much larger compared to macroscopic exchange field.« less

The quality of free antenatal and delivery services in Northern Sierra Leone.

PubMed

Koroma, Manso M; Kamara, Samuel S; Bangura, Evelyn A; Kamara, Mohamed A; Lokossou, Virgil; Keita, Namoudou

2017-07-12

The number of maternal deaths in sub-Saharan Africa continues to be overwhelmingly high. In West Africa, Sierra Leone leads the list, with the highest maternal mortality ratio. In 2010, financial barriers were removed as an incentive for more women to use available antenatal, delivery and postnatal services. Few published studies have examined the quality of free antenatal services and access to emergency obstetric care in Sierra Leone. A cross-sectional survey was conducted in 2014 in all 97 peripheral health facilities and three hospitals in Bombali District, Northern Region. One hundred antenatal care providers were interviewed, 276 observations were made and 486 pregnant women were interviewed. We assessed the adequacy of antenatal and delivery services provided using national standards. The distance was calculated between each facility providing delivery services and the nearest comprehensive emergency obstetric care (CEOC) facility, and the proportion of facilities in a chiefdom within 15 km of each CEOC facility was also calculated. A thematic map was developed to show inequities. The quality of services was poor. Based on national standards, only 27% of women were examined, 2% were screened on their first antenatal visit and 47% received interventions as recommended. Although 94% of facilities provided delivery services, a minority had delivery rooms (40%), delivery kits (42%) or portable water (46%). Skilled attendants supervised 35% of deliveries, and in only 35% of these were processes adequately documented. None of the five basic emergency obstetric care facilities were fully compliant with national standards, and the central and northernmost parts of the district had the least access to comprehensive emergency obstetric care. The health sector needs to monitor the quality of antenatal interventions in addition to measuring coverage. The quality of delivery services is compromised by poor infrastructure, inadequate skilled staff, stock-outs of

No Evidence for Lymphatic Filariasis Transmission in Big Cities Affected by Conflict Related Rural-Urban Migration in Sierra Leone and Liberia

PubMed Central

de Souza, Dziedzom K.; Sesay, Santigie; Moore, Marnijina G.; Ansumana, Rashid; Narh, Charles A.; Kollie, Karsor; Rebollo, Maria P.; Koudou, Benjamin G.; Koroma, Joseph B.; Bolay, Fatorma K.; Boakye, Daniel A.; Bockarie, Moses J.

2014-01-01

Background In West Africa, the principal vectors of lymphatic filariasis (LF) are Anopheles species with Culex species playing only a minor role in transmission, if any. Being a predominantly rural disease, the question remains whether conflict-related migration of rural populations into urban areas would be sufficient for active transmission of the parasite. Methodology/Principal Findings We examined LF transmission in urban areas in post-conflict Sierra Leone and Liberia that experienced significant rural-urban migration. Mosquitoes from Freetown and Monrovia, were analyzed for infection with Wuchereria bancrofti. We also undertook a transmission assessment survey (TAS) in Bo and Pujehun districts in Sierra Leone. The majority of the mosquitoes collected were Culex species, while Anopheles species were present in low numbers. The mosquitoes were analyzed in pools, with a maximum of 20 mosquitoes per pool. In both countries, a total of 1731 An. gambiae and 14342 Culex were analyzed for W. bancrofti, using the PCR. Two pools of Culex mosquitoes and 1 pool of An. gambiae were found infected from one community in Freetown. Pool screening analysis indicated a maximum likelihood of infection of 0.004 (95% CI of 0.00012–0.021) and 0.015 (95% CI of 0.0018–0.052) for the An. gambiae and Culex respectively. The results indicate that An. gambiae is present in low numbers, with a microfilaria prevalence breaking threshold value not sufficient to maintain transmission. The results of the TAS in Bo and Pujehun also indicated an antigen prevalence of 0.19% and 0.67% in children, respectively. This is well below the recommended 2% level for stopping MDA in Anopheles transmission areas, according to WHO guidelines. Conclusions We found no evidence for active transmission of LF in cities, where internally displaced persons from rural areas lived for many years during the more than 10 years conflict in Sierra Leone and Liberia. PMID:24516686

Peer-driven quality improvement among health workers and traditional birth attendants in Sierra Leone: linkages between providers' organizational skills and relationships.

PubMed

Higgins-Steele, Ariel; Waller, Kathryn; Fotso, Jean Christophe; Vesel, Linda

2015-01-01

Sierra Leone has among the poorest maternal and child health indicators in the world and investments in public health have been predominately to increase demand for services, with fewer initiatives targeting supply side factors that influence health workers' work environment. This paper uses data from the Quality Circles project in a rural district of Sierra Leone to achieve three objectives. First, we examine the effect of the intervention on organizational skills and relationships among coworkers as well as between health workers and traditional birth attendants. Second, we examine whether changes in organizational skills are associated with changes in relationships among and between formal and informal health providers and between health providers and clients. Third, we aim to further understand these changes through the perspectives of health workers and traditional birth attendants. The Quality Circles project was implemented in Kailahun District in the Eastern province of Sierra Leone from August 2011 to June 2013, with adjacent Tonkolili District serving as the control site. Using a mixed-methods approach, the evaluation included a quantitative survey, in-depth interviews and focus group discussions with health workers and traditional birth attendants. Mean values of the variables of interest were compared across sub-populations, and correlation analyses were performed between changes in organizational skills and changes in relationships. The results demonstrate that the Quality Circles intervention had positive effects on organizational skills and relationships. Furthermore, improvements in all organizational skill variables - problem-solving, strategizing and negotiation skills - were strongly associated with a change in the overall relationship variable. The Quality Circles approach has the potential to support health workers to improve their organizational skills and relationships, which in turn can contribute to improving the interpersonal dimensions of

Female Genital Mutilation in Sierra Leone: Forms, Reliability of Reported Status, and Accuracy of Related Demographic and Health Survey Questions

PubMed Central

Grant, Donald S.; Berggren, Vanja

2013-01-01

Objective. To determine forms of female genital mutilation (FGM), assess consistency between self-reported and observed FGM status, and assess the accuracy of Demographic and Health Surveys (DHS) FGM questions in Sierra Leone. Methods. This cross-sectional study, conducted between October 2010 and April 2012, enrolled 558 females aged 12–47 from eleven antenatal clinics in northeast Sierra Leone. Data on demography, FGM status, and self-reported anatomical descriptions were collected. Genital inspection confirmed the occurrence and extent of cutting. Results. All participants reported FGM status; 4 refused genital inspection. Using the WHO classification of FGM, 31.7% had type Ib; 64.1% type IIb; and 4.2% type IIc. There was a high level of agreement between reported and observed FGM prevalence (81.2% and 81.4%, resp.). There was no correlation between DHS FGM responses and anatomic extent of cutting, as 2.7% reported pricking; 87.1% flesh removal; and 1.1% that genitalia was sewn closed. Conclusion. Types I and II are the main forms of FGM, with labia majora alterations in almost 5% of cases. Self-reports on FGM status could serve as a proxy measurement for FGM prevalence but not for FGM type. The DHS FGM questions are inaccurate for determining cutting extent. PMID:24204384

Method for pulse control in a laser including a stimulated brillouin scattering mirror system

DOEpatents

Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

2007-10-23

A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Risk in the "Red Zone": Outcomes for Children Admitted to Ebola Holding Units in Sierra Leone Without Ebola Virus Disease.

PubMed

Fitzgerald, F; Wing, K; Naveed, A; Gbessay, M; Ross, J C G; Checchi, F; Youkee, D; Jalloh, M B; Baion, D; Mustapha, A; Jah, H; Lako, S; Oza, S; Boufkhed, S; Feury, R; Bielicki, J; Williamson, E; Gibb, D M; Klein, N; Sahr, F; Yeung, S

2017-07-01

We collected data on 1054 children admitted to Ebola Holding Units in Sierra Leone and describe outcomes of 697/1054 children testing negative for Ebola virus disease (EVD) and accompanying caregivers. Case-fatality was 9%; 3/630 (0.5%) children discharged testing negative were readmitted EVD-positive. Nosocomial EVD transmission risk may be lower than feared. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.

Deaths, late deaths, and role of infecting dose in Ebola virus disease in Sierra Leone: retrospective cohort study.

PubMed

Bower, Hilary; Smout, Elizabeth; Bangura, Mohamed S; Kamara, Osman; Turay, Cecilia; Johnson, Sembia; Oza, Shefali; Checchi, Francesco; Glynn, Judith R

2016-05-17

 To assess the frequency of fatal recrudescence from Ebola virus disease after discharge from treatment centres, and explore the influence of infecting dose on case fatality rates.  Retrospective cohort study.  Western Area, Sierra Leone.  151 survivors treated for Ebola virus disease at the Kerry Town treatment centre and discharged. Survivors were followed up for a vital status check at four to nine months after discharge, and again at six to 13 months after discharge. Verbal autopsies were conducted for four survivors who had died since discharge (that is, late deaths). Survivors still living in Western Area were interviewed together with their household members. Exposure level to Ebola virus disease was ascertained as a proxy of infecting dose, including for those who died.  Risks and causes of late death; case fatality rates; odds ratios of death from Ebola virus disease by age, sex, exposure level, date, occupation, and household risk factors.  Follow-up information was obtained on all 151 survivors of Ebola virus disease, a mean of 10 months after discharge. Four deaths occurred after discharge, all within six weeks: two probably due to late complications, one to prior tuberculosis, and only one after apparent full recovery, giving a maximum estimate of recrudescence leading to death of 0.7%. In these households, 395 people were reported to have had Ebola virus disease, of whom 227 died. A further 53 people fulfilled the case definition for probable disease, of whom 11 died. Therefore, the case fatality rate was 57.5% (227/395) for reported Ebola virus disease, or 53.1% (238/448) including probable disease. Case fatality rates were higher in children aged under 2 years and adults older than 30 years, in larger households, and in infections occurring earlier in the epidemic in Sierra Leone. There was no consistent trend of case fatality rate with exposure level, although increasing exposure increased the risk of Ebola virus disease.  In this study of

Separated-pair independent particle model and the generalized Brillouin theorem: ab initio calculations on the dissociation of polyatomic molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundberg, Kenneth Randall

1976-01-01

A method is developed to optimize the separated-pair independent particle (SPIP) wave function; it is a special case of the separated-pair theory obtained by using two-term natural expansions of the geminals. The orbitals are optimized by a theory based on the generalized Brillouin theorem and iterative configuration interaction (CI) calculations in the space of the SPIP function and its single excitations. The geminal expansion coefficients are optimized by serial 2 x 2 CI calculations. Formulas are derived for the matrix elements. An algorithm to implement the method is presented, and the work needed to evaluate the molecular integrals is discussed.

Role of Frequency Chirp and Energy Flow Directionality in the Strong Coupling Regime of Brillouin-Based Plasma Amplification.

PubMed

Chiaramello, M; Amiranoff, F; Riconda, C; Weber, S

2016-12-02

A detailed analysis is presented of the various stages of strong coupling Brillouin plasma amplification, emphasizing the importance of the chirp which can be of threefold origin: the intrinsic one driven by the amplification process, the one originating from the chirped-pulse-generated laser pulses, and the one associated with the plasma profile. Control of the overall chirp can optimize or quench the energy transfer. The time-dependent phase relation explains the energy flow direction during amplification and is characteristic for this strong coupling process. The study is also of potential importance to understand and maybe control cross-beam-energy transfer in inertial confinement fusion.

Herbal medicine use among hypertensive patients attending public and private health facilities in Freetown Sierra Leone.

PubMed

James, Peter Bai; Kamara, Halimatu; Bah, Abdulai Jawo; Steel, Amie; Wardle, Jon

2018-05-01

This study aimed to determine the prevalence, determinants and pattern of herbal medicine use among hypertensive patients in Freetown. We conducted a cross-sectional study among hypertensive patients attending public and private health facilities in Freetown, Sierra Leone between August and October 2016. We analyzed the data using SPSS version 24. We used Chi-square, Fisher exact two-tailed test and regression analysis for data analysis. A p-value less than 0.05 was considered statistically significant. Out of 260 study participants, over half (n = 148, 56.9%) reported using herbal medicine for the treatment of hypertension alone or together with comorbid condition(s). The most commonly used herbal medicine among users were honey (n = 89, 33.3%), moringa (n = 80, 30.0%) and garlic (n = 73, 27.3%). No significant difference existed between users and non-users of herbal medicine with regards to socio-demographic and health-related factors. The majority (n = 241, 92.7%) of respondents considered herbal medicine beneficial if it was recommended by a healthcare provider yet 85.1% (n = 126) did not disclose their herbal medicine use to their health care provider. There is a high use of herbal medicines among hypertensive patients in Freetown, Sierra Leone. It is essential for healthcare providers to take heed of the findings of this study and routinely ask their patients about their herbal medicine use status. Such practice will provide the opportunity to discuss the benefits and risks of herbal medicine use with the aim of maximizing patient desired therapeutic outcomes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Collective Sexual Violence in Bosnia and Sierra Leone: A Comparative Case Study Analysis.

PubMed

Ten Bensel, Tusty; Sample, Lisa L

2017-08-01

Social scientists have long studied the patterns, motivations, and recidivism rates of sexual offenders; however, the majority of prior research has examined rape, where victims are assaulted by a single offender in isolated events. Often overlooked are sexually violent assaults committed during armed conflicts, which often exhibit group-level sexual offending. This oversight could be a result of perceived notions that sexual violence during conflict is a rare or regrettable event; however, it has been documented consistently throughout history. The purpose of this study was to improve our understanding of sexual violence during war by comparing and contrasting preconflict characteristics, conflict framing, and justifications for sexual violence in the Bosnian and Sierra Leone armed conflicts. This greater understanding can then be used to identify factors that may contribute to the collectivization of sexual violence during war.

Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbiotti, G.; Tacchi, S.; Montoncello, F.

2015-06-29

The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained bymore » dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.« less

SAFARI digital processing unit: performance analysis of the SpaceWire links in case of a LEON3-FT based CPU

NASA Astrophysics Data System (ADS)

Giusi, Giovanni; Liu, Scige J.; Di Giorgio, Anna M.; Galli, Emanuele; Pezzuto, Stefano; Farina, Maria; Spinoglio, Luigi

2014-08-01

SAFARI (SpicA FAR infrared Instrument) is a far-infrared imaging Fourier Transform Spectrometer for the SPICA mission. The Digital Processing Unit (DPU) of the instrument implements the functions of controlling the overall instrument and implementing the science data compression and packing. The DPU design is based on the use of a LEON family processor. In SAFARI, all instrument components are connected to the central DPU via SpaceWire links. On these links science data, housekeeping and commands flows are in some cases multiplexed, therefore the interface control shall be able to cope with variable throughput needs. The effective data transfer workload can be an issue for the overall system performances and becomes a critical parameter for the on-board software design, both at application layer level and at lower, and more HW related, levels. To analyze the system behavior in presence of the expected SAFARI demanding science data flow, we carried out a series of performance tests using the standard GR-CPCI-UT699 LEON3-FT Development Board, provided by Aeroflex/Gaisler, connected to the emulator of the SAFARI science data links, in a point-to-point topology. Two different communication protocols have been used in the tests, the ECSS-E-ST-50-52C RMAP protocol and an internally defined one, the SAFARI internal data handling protocol. An incremental approach has been adopted to measure the system performances at different levels of the communication protocol complexity. In all cases the performance has been evaluated by measuring the CPU workload and the bus latencies. The tests have been executed initially in a custom low level execution environment and finally using the Real- Time Executive for Multiprocessor Systems (RTEMS), which has been selected as the operating system to be used onboard SAFARI. The preliminary results of the carried out performance analysis confirmed the possibility of using a LEON3 CPU processor in the SAFARI DPU, but pointed out, in agreement

Strengthening pre-service training for skilled birth attendance - An evaluation of the maternal and child health aide training programme in Sierra Leone.

PubMed

Jones, Susan A; Sam, Betty; Bull, Florence; James, Margaret; Ameh, Charles A; van den Broek, Nynke R

2016-06-01

The high maternal mortality rate in Sierra Leone combined with an ongoing shortage of midwives has led to the introduction of new cadres of healthcare workers. Maternal and Child Health Aides are one such cadre and now provide 56% of patient care. The quality of the education training programme for MCHA is therefore of paramount importance if high quality maternal care is to be provided. To conduct an evaluation of the MCHAide training programme in Sierra Leone. Mapping of programme and focus group discussions (FGDs) with key informants. Analysis of data using a thematic approach and formulation of recommendations for national, district and individual levels. All 14 MCHAide schools across Sierra Leone. The National Coordinator, Coordinators from 14 MCHAide schools and District Health Sisters from District Health Management Teams. Focus group discussions were held with tutors facilitated by a group member to encourage a free flowing discussion. Participants were divided into 4 groups, one for each province, with 5-8 participants per group and 50min for the discussion. Strengths, weaknesses and opportunities of the MCHAide training programme were identified. Four major themes were identified; the need for autonomy and support within the programme from stakeholders; the effect of poor infrastructure on teaching and student learning; the need to ensure rigorous academic quality including teaching quality, curricula content and the academic ability of the students; and the benefits of community support. It is important that the key personnel be involved in the development and introduction of training programmes for new cadres of staff from the earliest stages of development. On-going programme review and development is essential and those implementing the programme are the best placed to lead and contribute to this. Gathering the experiences and perceptions of key informants helps provide an in-depth examination that can inform recommendations. Copyright © 2016 The

Bayesian inference in an extended SEIR model with nonparametric disease transmission rate: an application to the Ebola epidemic in Sierra Leone.

PubMed

Frasso, Gianluca; Lambert, Philippe

2016-10-01

SummaryThe 2014 Ebola outbreak in Sierra Leone is analyzed using a susceptible-exposed-infectious-removed (SEIR) epidemic compartmental model. The discrete time-stochastic model for the epidemic evolution is coupled to a set of ordinary differential equations describing the dynamics of the expected proportions of subjects in each epidemic state. The unknown parameters are estimated in a Bayesian framework by combining data on the number of new (laboratory confirmed) Ebola cases reported by the Ministry of Health and prior distributions for the transition rates elicited using information collected by the WHO during the follow-up of specific Ebola cases. The time-varying disease transmission rate is modeled in a flexible way using penalized B-splines. Our framework represents a valuable stochastic tool for the study of an epidemic dynamic even when only irregularly observed and possibly aggregated data are available. Simulations and the analysis of the 2014 Sierra Leone Ebola data highlight the merits of the proposed methodology. In particular, the flexible modeling of the disease transmission rate makes the estimation of the effective reproduction number robust to the misspecification of the initial epidemic states and to underreporting of the infectious cases. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

G6PD deficiency assessment in Freetown, Sierra Leone, reveals further insight into the molecular heterogeneity of G6PD A-.

PubMed

Jalloh, Amadu; Jalloh, Muctarr; Gamanga, Idrissa; Baion, David; Sahr, Foday; Gbakima, Aiah; Willoughby, Victor R; Matsuoka, Hiroyuki

2008-01-01

Glucose-6-phosphate dehydrogenase (G6PD) deficiency in Africa is of high prevalence, although precise data are lacking in many individual nations. We investigated 129 unrelated subjects (71 male subjects, 58 female subjects) visiting a teaching hospital in Freetown, Sierra Leone, to collect baseline data on the distribution of G6PD deficiency among respective ethnic groups in the country. We confirmed eight G6PD-deficient male subjects by two formazan-based blood tests (11.3% of the male subjects examined), and also detected the common 376A > G mutation in 11 male subjects and eight female subjects by sequencing exons 3-5 of the G6PD gene. Selected samples were further sequenced for exons 2-13 and introns 5, 7, 8, and 11. Among the deficient male subjects, six were G6PD A- carrying the double mutations (202G > A and 376A > G), all of whom were in the Temne and Mende ethnic groups. Others included A- Betica, and a novel variant having double mutations in exon 5 (311G > A and 376A > G forming 104 Arg > His and 126 Asn > Asp, respectively), which we designate as G6PD Sierra Leone. Subsequent haplotype analysis linked this novel variant to the G6PD A- "family".

Context matters: community characteristics and mental health among war-affected youth in Sierra Leone.

PubMed

Betancourt, Theresa S; McBain, Ryan; Newnham, Elizabeth A; Brennan, Robert T

2014-03-01

Worldwide, over one billion children and adolescents live in war-affected settings. At present, only limited research has investigated linkages between disrupted social ecology and adverse mental health outcomes among war-affected youth. In this study, we examine three community-level characteristics - social disorder and collective efficacy within the community, as reported by caregivers, and perceived stigma as reported by youth - in relation to externalizing behaviors and internalizing symptoms among male and female former child soldiers in postconflict Sierra Leone. A total of 243 former child soldiers (30% female, mean age at baseline: 16.6 years) and their primary caregivers participated in interviews in 2004 and 2008, as part of a larger prospective cohort study of war-affected youth in Sierra Leone. Two-point growth models were estimated to examine the relationship between community-level characteristics and externalizing and internalizing outcomes across the time points. Both social disorder within the community, reported by caregivers, and perceived stigma, reported by youth, positively covaried with youths' externalizing and internalizing scores - indicating that higher levels of each at baseline and follow-up were associated with higher levels of mental health problems at both time points (p < .05). The relationship between collective efficacy and mental health outcomes was nonsignificant (p > .05). This study offers a rare glimpse into the role that the postconflict social context plays in shaping the mental health among former child soldiers. Results indicate that both social disorder and perceived stigma within the community demonstrate an important relationship to externalizing and internalizing problems among adolescent ex-combatants. Moreover, these relationships persisted over a 4-year period of follow-up. These results underscore the importance of the postconflict social environment and the need to develop postconflict interventions that

Sequelae and Other Conditions in Ebola Virus Disease Survivors, Sierra Leone, 2015.

PubMed

Mohammed, Hamish; Vandy, Alren O; Stretch, Rebecca; Otieno, David; Prajapati, Mukesh; Calderon, Mauricio; Vandi, Mohamed

2017-01-01

We rapidly assessed the health of Ebola virus disease (EVD) survivors in Kenema, Sierra Leone, by reviewing medical charts of all patients attending the Survivor Clinic of Kenema Government Hospital. Data were abstracted on signs and symptoms at every attendance. As of November 2015, a total of 621 attendances by 115 survivors with laboratory-confirmed EVD were made to the Survivor Clinic. Most (60.9%) survivors were women. Survivors' median age was 28 years (range 0.25-70 years). Survivors attended the clinic a median of 5 times (range 1-21 times) each, and the median time from EVD discharge to attendance was 261 days (range 4-504 days). The most commonly reported signs and symptoms among the 621 attendances were headache (63.1%), fever (61.7%), and myalgia (43.3%). Because health needs of EVD survivors are complex, rapid chart reviews at survivor clinics should be repeated regularly to assess the extent of illness and prioritize service delivery.

Generalized symmetries of an 𝓝 = 1 supersymmetric Boiti-Leon-Manna-Pempinelli system

NASA Astrophysics Data System (ADS)

Wang, Jian-Yong; Tang, Xiao-Yan; Liang, Zu-Feng; Lou, Sen-Yue

2015-05-01

The formal series symmetry approach (FSSA), a quite powerful and straightforward method to establish infinitely many generalized symmetries of classical integrable systems, has been successfully extended in the supersymmetric framework to explore series of infinitely many generalized symmetries for supersymmetric systems. Taking the 𝒩 = 1 supersymmetric Boiti-Leon-Manna-Pempinelli system as a concrete example, it is shown that the application of the extended FSSA to this supersymmetric system leads to a set of infinitely many generalized symmetries with an arbitrary function f (t). Some interesting special cases of symmetry algebras are presented, including a limit case f (t) = 1 related to the commutativity of higher order generalized symmetries. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275123, 11175092, 11475052, and 11435005), the Shanghai Knowledge Service Platform for Trustworthy Internet of Things, China (Grant No. ZF1213), and the Talent Fund and K CWong Magna Fund in Ningbo University, China.

Standard deviation index for stimulated Brillouin scattering suppression with different homogeneities.

PubMed

Ran, Yang; Su, Rongtao; Ma, Pengfei; Wang, Xiaolin; Zhou, Pu; Si, Lei

2016-05-10

We present a new quantitative index of standard deviation to measure the homogeneity of spectral lines in a fiber amplifier system so as to find the relation between the stimulated Brillouin scattering (SBS) threshold and the homogeneity of the corresponding spectral lines. A theoretical model is built and a simulation framework has been established to estimate the SBS threshold when input spectra with different homogeneities are set. In our experiment, by setting the phase modulation voltage to a constant value and the modulation frequency to different values, spectral lines with different homogeneities can be obtained. The experimental results show that the SBS threshold increases negatively with the standard deviation of the modulated spectrum, which is in good agreement with the theoretical results. When the phase modulation voltage is confined to 10 V and the modulation frequency is set to 80 MHz, the standard deviation of the modulated spectrum equals 0.0051, which is the lowest value in our experiment. Thus, at this time, the highest SBS threshold has been achieved. This standard deviation can be a good quantitative index in evaluating the power scaling potential in a fiber amplifier system, which is also a design guideline in suppressing the SBS to a better degree.

Using evidence to strengthen accountability for health financing in Sierra Leone.

PubMed

Lebbie, Sowo A; Le Voir, Rosanna; Tom-Kargbo, Joanna; Yilla, Mohamed Drissa; Kamara, Abu Bakarr; Nam, Sara L

2016-12-01

In 2012, the government of Sierra Leone cut the national budget allocation to the health sector. Civil society organizations planned a nationwide health budget advocacy campaign, coinciding with the 2012 general elections, to hold future leaders to account on financing for women's and children's health. As part of the campaign, Evidence for Action produced district health budget tracking scorecards. The scorecards presented Ministry of Finance data on the allocation and disbursement of health funds in each district. The data were communicated using simple, non-technical language so that citizens could understand the key messages and take action. A total of 5600 scorecards were shared at district electoral forums attended by political candidates, community members, and health activists. Since the election, the proportion of the total government budget allocated to health increased from 7.4% in 2012 to 11.2% in 2014. However, transforming politicians' commitments and pledges into implementation has been challenging, confirming that accountability is a long-term process. Copyright © 2016 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

Coherent Rayleigh-Brillouin scattering measurements of bulk viscosity of polar and nonpolar gases, and kinetic theory.

PubMed

Meijer, A S; de Wijn, A S; Peters, M F E; Dam, N J; van de Water, W

2010-10-28

We investigate coherent Rayleigh-Brillouin spectroscopy as an efficient process to measure the bulk viscosity of gases at gigahertz frequencies. Scattered spectral distributions are measured using a Fizeau spectrometer. We discuss the statistical error due to the fluctuating mode structure of the used pump laser. Experiments were done for both polar and nonpolar gases and the bulk viscosity was obtained from the spectra using the Tenti S6 model. Results are compared to simple classical kinetic models of molecules with internal degrees of freedom. At the extremely high (gigahertz) frequencies of our experiment, most internal vibrational modes remain frozen and the bulk viscosity is dominated by the rotational degrees of freedom. Our measurements show that the molecular dipole moments have unexpectedly little influence on the bulk viscosity at room temperature and moderate pressure.

Dynamical transition between weak and strong coupling in Brillouin laser pulse amplification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schluck, F.; Lehmann, G.; Müller, C.

Short laser pulse amplification via stimulated Brillouin backscattering in plasma is considered. Previous work distinguishes between the weakly and strongly coupled regime and treats them separately. It is shown here that such a separation is not generally applicable because strong and weak coupling interaction regimes are entwined with each other. An initially weakly coupled amplification scenario may dynamically transform into strong coupling. This happens when the local seed amplitude grows and thus triggers the strongly driven plasma response. On the other hand, when in a strong coupling scenario, the pump pulse gets depleted, and its amplitude might drop below themore » strong coupling threshold. This may cause significant changes in the final seed pulse shape. Furthermore, experimentally used pump pulses are typically Gaussian-shaped. The intensity threshold for strong coupling may only be exceeded around the maximum and not in the wings of the pulse. Also here, a description valid in both strong and weak coupling regimes is required. We propose such a unified treatment which allows us, in particular, to study the dynamic transition between weak and strong coupling. Consequences for the pulse forms of the amplified seed are discussed.« less

Ebola Surveillance - Guinea, Liberia, and Sierra Leone.

PubMed

McNamara, Lucy A; Schafer, Ilana J; Nolen, Leisha D; Gorina, Yelena; Redd, John T; Lo, Terrence; Ervin, Elizabeth; Henao, Olga; Dahl, Benjamin A; Morgan, Oliver; Hersey, Sara; Knust, Barbara

2016-07-08

Developing a surveillance system during a public health emergency is always challenging but is especially so in countries with limited public health infrastructure. Surveillance for Ebola virus disease (Ebola) in the West African countries heavily affected by Ebola (Guinea, Liberia, and Sierra Leone) faced numerous impediments, including insufficient numbers of trained staff, community reticence to report cases and contacts, limited information technology resources, limited telephone and Internet service, and overwhelming numbers of infected persons. Through the work of CDC and numerous partners, including the countries' ministries of health, the World Health Organization, and other government and nongovernment organizations, functional Ebola surveillance was established and maintained in these countries. CDC staff were heavily involved in implementing case-based surveillance systems, sustaining case surveillance and contact tracing, and interpreting surveillance data. In addition to helping the ministries of health and other partners understand and manage the epidemic, CDC's activities strengthened epidemiologic and data management capacity to improve routine surveillance in the countries affected, even after the Ebola epidemic ended, and enhanced local capacity to respond quickly to future public health emergencies. However, the many obstacles overcome during development of these Ebola surveillance systems highlight the need to have strong public health, surveillance, and information technology infrastructure in place before a public health emergency occurs. Intense, long-term focus on strengthening public health surveillance systems in developing countries, as described in the Global Health Security Agenda, is needed.The activities summarized in this report would not have been possible without collaboration with many U.S and international partners (http://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/partners.html).

Iodine Status of Women of Reproductive Age in Sierra Leone and Its Association with Household Coverage with Adequately Iodized Salt

PubMed Central

Rohner, Fabian; Wirth, James P.; Woodruff, Bradley A.; Chiwile, Faraja; Yankson, Hannah; Sesay, Fatmata; Koroma, Aminata S.; Petry, Nicolai; Pyne-Bailey, Solade; Dominguez, Elisa; Kupka, Roland; Hodges, Mary H.; de Onis, Mercedes

2016-01-01

Salt iodization programs are a public health success in tackling iodine deficiency. Yet, a large proportion of the world’s population remains at risk for iodine deficiency. In a nationally representative cross-sectional survey in Sierra Leone, household salt samples and women’s urine samples were quantitatively analyzed for iodine content. Salt was collected from 1123 households, and urine samples from 817 non-pregnant and 154 pregnant women. Household coverage with adequately iodized salt (≥15 mg/kg iodine) was 80.7%. The median urinary iodine concentration (UIC) of pregnant women was 175.8 µg/L and of non-pregnant women 190.8 µg/L. Women living in households with adequately iodized salt had higher median UIC (for pregnant women: 180.6 µg/L vs. 100.8 µg/L, respectively, p < 0.05; and for non-pregnant women: 211.3 µg/L vs. 97.8 µg/L, p < 0.001). Differences in UIC by residence, region, household wealth, and women’s education were much smaller in women living in households with adequately iodized salt than in households without. Despite the high household coverage of iodized salt in Sierra Leone, it is important to reach the 20% of households not consuming adequately iodized salt. Salt iodization has the potential for increasing equity in iodine status even with the persistence of other risk factors for deficiency. PMID:26848685

Brillouin-scattering studies of a sodium silicate glass in solid and melt conditions at temperatures up to 1000 °C

NASA Astrophysics Data System (ADS)

Xu, Ji-An; Manghnani, Murli H.

1992-01-01

By using the sapphire-glass-sapphire sandwich-glass-assemblage Brillouin-scattering technique, the velocities of shear and longitudinal modes of a sodium silicate glass have been measured as a function of temperature up to 1000 °C. A turning point was found at the strain point (494 °C) but not at the softening point (720 °C). Combined with the results of the 90°- and 180°-scattering-geometry measurements, the refractive index (n) of the glass as a function of temperature was also determined. As a result, independent criteria for both the strain and softening points are suggested.

Sierra Leone's Former Child Soldiers: A Follow-up Study of Psychosocial Adjustment and Community Reintegration

PubMed Central

Betancourt, Theresa Stichick; Borisova, Ivelina Ivanova; Williams, Timothy Philip; Brennan, Robert T.; Whitfield, T. Hatch; de la Soudiere, Marie; Williamson, John; Gilman, Stephen E.

2009-01-01

This is the first prospective study to investigate psychosocial adjustment in male and female former child soldiers (n=156, 12% female). The study began in Sierra Leone in 2002 and was designed to examine both risk and protective factors in psychosocial adjustment. Over the two-year period of follow up, youth who had wounded or killed others during the war demonstrated increases in hostility. Youth who survived rape had higher levels of anxiety and hostility, but also demonstrated greater confidence and prosocial attitudes at follow up. Of the potential protective resources examined, improved community acceptance was associated with reduced depression at follow up and improved confidence and prosocial attitudes regardless of levels of violence exposure. Retention in school was also associated with greater prosocial attitudes. PMID:20636683

National survey of Ebola-related knowledge, attitudes and practices before the outbreak peak in Sierra Leone: August 2014

PubMed Central

Jalloh, Mohamed F; Sengeh, Paul; Monasch, Roeland; Jalloh, Mohammad B; DeLuca, Nickolas; Dyson, Meredith; Golfa, Sheku; Sakurai, Yukiko; Conteh, Lansana; Sesay, Samuel; Brown, Vance; Li, Wenshu; Mermin, Jonathan; Bunnell, Rebecca

2017-01-01

Background The 2014–2015 Ebola epidemic in West Africa was the largest ever to occur. In the early phases, little was known about public knowledge, attitudes and practices (KAP) relating to Ebola virus disease (Ebola). Data were needed to develop evidence-driven strategies to address gaps in knowledge and practice. Methods In August 2014, we conducted interviews with 1413 randomly selected respondents from 9 out of 14 districts in Sierra Leone using multistage cluster sampling. Where suitable, Ebola-related KAP questions were adapted from other internationally validated questionnaires related to infectious diseases. Results All respondents were aware of Ebola. When asked unprompted, 60% of respondents could correctly cite fever, diarrhoea and vomiting as signs/symptoms of Ebola. A majority of respondents knew that avoiding infected blood and bodily fluids (87%) and contact with an infected corpse (85%) could prevent Ebola. However, there were also widespread misconceptions such as the belief that Ebola can be prevented by washing with salt and hot water (41%). Almost everyone interviewed (95%) expressed at least one discriminatory attitude towards Ebola survivors. Unprompted, self-reported actions taken to avoid Ebola infection included handwashing with soap (66%) and avoiding physical contact with patients with suspected Ebola (40%). Conclusion Three months into the 2014 Ebola outbreak in Sierra Leone, our findings suggest there was high awareness of the disease but misconceptions and discriminatory attitudes toward survivors remained common. These findings directly informed the development of a national social mobilisation strategy and demonstrated the importance of KAP assessment early in an epidemic. PMID:29259820

Microbiological and Chemical Quality of Packaged Sachet Water and Household Stored Drinking Water in Freetown, Sierra Leone

PubMed Central

Jalloh, Mohamed F.; Saquee, George; Bain, Robert E. S.; Bartram, Jamie K.

2015-01-01

Packaged drinking water (PW) sold in bottles and plastic bags/sachets is widely consumed in low- and middle-income countries (LMICs), and many urban users in sub-Saharan Africa (SSA) rely on packaged sachet water (PSW) as their primary source of water for consumption. However, few rigorous studies have investigated PSW quality in SSA, and none have compared PSW to stored household water for consumption (HWC). A clearer understanding of PSW quality in the context of alternative sources is needed to inform policy and regulation. As elsewhere in SSA, PSW is widely consumed in Sierra Leone, but government oversight is nearly nonexistent. This study examined the microbiological and chemical quality of a representative sample of PSW products in Freetown, Sierra Leone at packaged water manufacturing facilities (PWMFs) and at points of sale (POSs). Samples of HWC were also analyzed for comparison. The study did not find evidence of serious chemical contamination among the parameters studied. However, 19% of 45 PSW products sampled at the PWMF contained detectable Escherichia coli (EC), although only two samples exceeded 10 CFU/100 mL. Concentrations of total coliforms (TC) in PSW (but not EC) increased along the supply chain. Samples of HWC from 60 households in Freetown were significantly more likely to contain EC and TC than PSW at the point of production (p<0.01), and had significantly higher concentrations of both bacterial indicators (p<0.01). These results highlight the need for additional PSW regulation and surveillance, while demonstrating the need to prioritize the safety of HWC. At present, PSW may be the least unsafe option for many households. PMID:26162082

Microbiological and Chemical Quality of Packaged Sachet Water and Household Stored Drinking Water in Freetown, Sierra Leone.

PubMed

Fisher, Michael B; Williams, Ashley R; Jalloh, Mohamed F; Saquee, George; Bain, Robert E S; Bartram, Jamie K

2015-01-01

Packaged drinking water (PW) sold in bottles and plastic bags/sachets is widely consumed in low- and middle-income countries (LMICs), and many urban users in sub-Saharan Africa (SSA) rely on packaged sachet water (PSW) as their primary source of water for consumption. However, few rigorous studies have investigated PSW quality in SSA, and none have compared PSW to stored household water for consumption (HWC). A clearer understanding of PSW quality in the context of alternative sources is needed to inform policy and regulation. As elsewhere in SSA, PSW is widely consumed in Sierra Leone, but government oversight is nearly nonexistent. This study examined the microbiological and chemical quality of a representative sample of PSW products in Freetown, Sierra Leone at packaged water manufacturing facilities (PWMFs) and at points of sale (POSs). Samples of HWC were also analyzed for comparison. The study did not find evidence of serious chemical contamination among the parameters studied. However, 19% of 45 PSW products sampled at the PWMF contained detectable Escherichia coli (EC), although only two samples exceeded 10 CFU/100 mL. Concentrations of total coliforms (TC) in PSW (but not EC) increased along the supply chain. Samples of HWC from 60 households in Freetown were significantly more likely to contain EC and TC than PSW at the point of production (p<0.01), and had significantly higher concentrations of both bacterial indicators (p<0.01). These results highlight the need for additional PSW regulation and surveillance, while demonstrating the need to prioritize the safety of HWC. At present, PSW may be the least unsafe option for many households.

Phase transition in lead titanate thin films: a Brillouin study

NASA Astrophysics Data System (ADS)

Kuzel, P.; Dugautier, C.; Moch, P.; LeMarrec, F.; Karkut, M. G.

2002-12-01

The elastic properties of both polycrystalline and epitaxial PbTiO3 (PTO) thin films are studied using Brillouin scattering spectroscopy. The epitaxial PTO films were prepared by pulsed laser ablation on (1) a [0 0 1] single crystal of SrTiO3 (STO) doped with Nb and (2) a [0 0 1] STO buffered with a layer of YBa2Cu3O7. The polycrystalline PTO films were prepared by sol-gel on a Si substrate buffered with TiO2 and Pt layers. The data analysis takes into account the ripple and the elasto-optic contributions. The latter significantly affects the measured spectra since it gives rise to a Love mode in the p-s scattering geometry. At room temperature, the spectra of the epitaxially grown samples are interpreted using previously published elastic constants of PTO single crystals. Sol-gel samples exhibit appreciable softening of the effective elastic properties compared to PTO single crystals: this result is explained by taking into account the random orientation of the microscopic PTO grains. For both the polycrystalline and the epitaxial films we have determined that the piezoelectric terms do not contribute to the spectra. The temperature dependence of the spectra shows strong anomalies of the elastic properties near the ferroelectric phase transition. Compared to the bulk, TC is higher in the sol-gel films, while in the epitaxial films the sign of the TC shift depends on the underlying material.

Coherent beam combination using self-phase locked stimulated Brillouin scattering phase conjugate mirrors with a rotating wedge for high power laser generation.

PubMed

Park, Sangwoo; Cha, Seongwoo; Oh, Jungsuk; Lee, Hwihyeong; Ahn, Heekyung; Churn, Kil Sung; Kong, Hong Jin

2016-04-18

The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers. We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM. Its phase locking ability and the usefulness on the beam-combination laser are demonstrated experimentally. A four-beam combination is demonstrated using this SBS-PCM scheme. The relative phases between the beams were measured to be less than λ/24.7.